// SPDX-License-Identifier: GPL-2.0+
/*
 *  Base port operations for 8250/16550-type serial ports
 *
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *  Split from 8250_core.c, Copyright (C) 2001 Russell King.
 *
 * A note about mapbase / membase
 *
 *  mapbase is the physical address of the IO port.
 *  membase is an 'ioremapped' cookie.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/gpio/consumer.h>
#include <linux/sysrq.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/tty.h>
#include <linux/ratelimit.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/serial_8250.h>
#include <linux/nmi.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/pm_runtime.h>
#include <linux/ktime.h>

#include <asm/io.h>
#include <asm/irq.h>

#include "8250.h"

/* Nuvoton NPCM timeout register */
#define UART_NPCM_TOR 7
#define UART_NPCM_TOIE BIT(7) /* Timeout Interrupt Enable */

/*
 * Debugging.
 */
#define DEBUG_AUTOCONF(fmt...)                                                                                         \
    do {                                                                                                               \
    } while (0)

#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)

#define PORT_ONE 1
#define PORT_FOUR 4
#define PORT_FIVE 5
#define PORT_SIX 6
#define PORT_SEVEN 7
#define PORT_EIGHT 8
#define PORT_FOURTEEN 14
#define PORT_SIXTEEN 16
#define PORT_TWENTYFOUR 24
#define PORT_TWENTYEIGHT 28
#define PORT_THIRTY 30
#define PORT_THIRTYTWO 32
#define PORT_FIFTYSIX 56
#define PORT_SIXTY 60
#define PORT_SIXTYTWO 62
#define PORT_SIXTYTHREE 63
#define PORT_SIXTYFOUR 64
#define PORT_ONEHUNDREDTWELVE 112
#define PORT_ONEHUNDREDTWENTY 120
#define PORT_ONEHUNDREDTWENTYSIX 126
#define PORT_ONEHUNDREDTWENTYEIGHT 128
#define PORT_ONEHUNDREDFIFTYSIX 256
#define PORT_ONETHOUSAND 1000
#define PORT_ONETHOUSANDTWENTYFOUR 1024
#define PORT_TENTHOUSAND 10000
#define PORT_ONETHOUSANDTHOUSAND 1000000
/*
 * Here we define the default xmit fifo size used for each type of UART.
 */
static const struct serial8250_config uart_config[] = {
    [PORT_UNKNOWN] = {
        .name = "unknown",
        .fifo_size = PORT_ONE,
        .tx_loadsz = PORT_ONE,
    },
    [PORT_8250] = {
        .name = "8250",
        .fifo_size = PORT_ONE,
        .tx_loadsz = PORT_ONE,
    },
    [PORT_16450] = {
        .name = "16450",
        .fifo_size = PORT_ONE,
        .tx_loadsz = PORT_ONE,
    },
    [PORT_16550] = {
        .name = "16550",
        .fifo_size = PORT_ONE,
        .tx_loadsz = PORT_ONE,
    },
    [PORT_16550A] = {
        .name = "16550A",
        .fifo_size = PORT_SIXTEEN,
        .tx_loadsz = PORT_SIXTEEN,
        .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
        .rxtrig_bytes = {PORT_ONE, PORT_FOUR, PORT_EIGHT, PORT_FOURTEEN},
        .flags = UART_CAP_FIFO,
    },
    [PORT_CIRRUS] = {
        .name = "Cirrus",
        .fifo_size = PORT_ONE,
        .tx_loadsz = PORT_ONE,
    },
    [PORT_16650] = {
        .name = "ST16650",
        .fifo_size = PORT_ONE,
        .tx_loadsz = PORT_ONE,
        .flags = UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
    },
    [PORT_16650V2] = {
        .name = "ST16650V2",
        .fifo_size = PORT_THIRTYTWO,
        .tx_loadsz = PORT_SIXTEEN,
        .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01 | UART_FCR_T_TRIG_00,
        .rxtrig_bytes = {8, PORT_SIXTEEN, PORT_TWENTYFOUR, PORT_TWENTYEIGHT},
        .flags = UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
    },
    [PORT_16750] = {
        .name = "TI16750",
        .fifo_size = PORT_SIXTYFOUR,
        .tx_loadsz = PORT_SIXTYFOUR,
        .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10 | UART_FCR7_64BYTE,
        .rxtrig_bytes = {PORT_ONE, PORT_SIXTEEN, PORT_THIRTYTWO, PORT_FIFTYSIX},
        .flags = UART_CAP_FIFO | UART_CAP_SLEEP | UART_CAP_AFE,
    },
    [PORT_STARTECH] = {
        .name = "Startech",
        .fifo_size = PORT_ONE,
        .tx_loadsz = PORT_ONE,
    },
    [PORT_16C950] = {
        .name = "16C950/954",
        .fifo_size = PORT_ONEHUNDREDTWENTYEIGHT,
        .tx_loadsz = PORT_ONEHUNDREDTWENTYEIGHT,
        .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01,
        .rxtrig_bytes = {PORT_SIXTEEN, PORT_THIRTYTWO, PORT_ONEHUNDREDTWELVE, PORT_ONEHUNDREDTWENTY},
        /* UART_CAP_EFR breaks billionon CF bluetooth card. */
        .flags = UART_CAP_FIFO | UART_CAP_SLEEP,
    },
    [PORT_16654] = {
        .name = "ST16654",
        .fifo_size = PORT_SIXTYFOUR,
        .tx_loadsz = PORT_THIRTYTWO,
        .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01 | UART_FCR_T_TRIG_10,
        .rxtrig_bytes = {PORT_EIGHT, PORT_SIXTEEN, PORT_FIFTYSIX, PORT_SIXTY},
        .flags = UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
    },
    [PORT_16850] = {
        .name = "XR16850",
        .fifo_size = PORT_ONEHUNDREDTWENTYEIGHT,
        .tx_loadsz = PORT_ONEHUNDREDTWENTYEIGHT,
        .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
        .flags = UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
    },
    [PORT_RSA] = {
        .name = "RSA",
        .fifo_size = 2048,
        .tx_loadsz = 2048,
        .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_11,
        .flags = UART_CAP_FIFO,
    },
    [PORT_NS16550A] = {
        .name = "NS16550A",
        .fifo_size = PORT_SIXTEEN,
        .tx_loadsz = PORT_SIXTEEN,
        .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
        .flags = UART_CAP_FIFO | UART_NATSEMI,
    },
    [PORT_XSCALE] = {
        .name = "XScale",
        .fifo_size = PORT_THIRTYTWO,
        .tx_loadsz = PORT_THIRTYTWO,
        .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
        .flags = UART_CAP_FIFO | UART_CAP_UUE | UART_CAP_RTOIE,
    },
    [PORT_OCTEON] =
        {
            .name = "OCTEON",
            .fifo_size = PORT_SIXTYFOUR,
            .tx_loadsz = PORT_SIXTYFOUR,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
            .flags = UART_CAP_FIFO,
        },
    [PORT_AR7] =
        {
            .name = "AR7",
            .fifo_size = PORT_SIXTEEN,
            .tx_loadsz = PORT_SIXTEEN,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_00,
            .flags = UART_CAP_FIFO /* | UART_CAP_AFE */,
        },
    [PORT_U6_16550A] =
        {
            .name = "U6_16550A",
            .fifo_size = PORT_SIXTYFOUR,
            .tx_loadsz = PORT_SIXTYFOUR,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
            .flags = UART_CAP_FIFO | UART_CAP_AFE,
        },
    [PORT_TEGRA] =
        {
            .name = "Tegra",
            .fifo_size = PORT_THIRTYTWO,
            .tx_loadsz = PORT_EIGHT,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01 | UART_FCR_T_TRIG_01,
            .rxtrig_bytes = {PORT_ONE, PORT_FOUR, PORT_EIGHT, PORT_FOURTEEN},
            .flags = UART_CAP_FIFO | UART_CAP_RTOIE,
        },
    [PORT_XR17D15X] =
        {
            .name = "XR17D15X",
            .fifo_size = PORT_SIXTYFOUR,
            .tx_loadsz = PORT_SIXTYFOUR,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
            .flags = UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR | UART_CAP_SLEEP,
        },
    [PORT_XR17V35X] =
        {
            .name = "XR17V35X",
            .fifo_size = PORT_ONEHUNDREDFIFTYSIX,
            .tx_loadsz = PORT_ONEHUNDREDFIFTYSIX,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_11 | UART_FCR_T_TRIG_11,
            .flags = UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR | UART_CAP_SLEEP,
        },
    [PORT_LPC3220] =
        {
            .name = "LPC3220",
            .fifo_size = PORT_SIXTYFOUR,
            .tx_loadsz = PORT_THIRTYTWO,
            .fcr = UART_FCR_DMA_SELECT | UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_00 | UART_FCR_T_TRIG_00,
            .flags = UART_CAP_FIFO,
        },
    [PORT_BRCM_TRUMANAGE] =
        {
            .name = "TruManage",
            .fifo_size = PORT_ONE,
            .tx_loadsz = PORT_ONETHOUSANDTWENTYFOUR,
            .flags = UART_CAP_HFIFO,
        },
    [PORT_8250_CIR] = {.name = "CIR port"},
    [PORT_ALTR_16550_F32] =
        {
            .name = "Altera 16550 FIFO32",
            .fifo_size = PORT_THIRTYTWO,
            .tx_loadsz = PORT_THIRTYTWO,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
            .rxtrig_bytes = {PORT_ONE, PORT_EIGHT, PORT_SIXTEEN, PORT_THIRTY},
            .flags = UART_CAP_FIFO | UART_CAP_AFE,
        },
    [PORT_ALTR_16550_F64] =
        {
            .name = "Altera 16550 FIFO64",
            .fifo_size = PORT_SIXTYFOUR,
            .tx_loadsz = PORT_SIXTYFOUR,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
            .rxtrig_bytes = {PORT_ONE, PORT_SIXTEEN, PORT_THIRTYTWO, PORT_SIXTYTWO},
            .flags = UART_CAP_FIFO | UART_CAP_AFE,
        },
    [PORT_ALTR_16550_F128] =
        {
            .name = "Altera 16550 FIFO128",
            .fifo_size = PORT_ONEHUNDREDTWENTYEIGHT,
            .tx_loadsz = PORT_ONEHUNDREDTWENTYEIGHT,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
            .rxtrig_bytes = {PORT_ONE, PORT_THIRTYTWO, PORT_SIXTYFOUR, PORT_ONEHUNDREDTWENTYSIX},
            .flags = UART_CAP_FIFO | UART_CAP_AFE,
        },
    /*
        * tx_loadsz is set to 63-bytes instead of 64-bytes to implement
        * workaround of errata A-008006 which states that tx_loadsz should
        * be configured less than Maximum supported fifo bytes.
        */
    [PORT_16550A_FSL64] =
        {
            .name = "16550A_FSL64",
            .fifo_size = PORT_SIXTYFOUR,
            .tx_loadsz = PORT_SIXTYTHREE,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10 | UART_FCR7_64BYTE,
            .flags = UART_CAP_FIFO,
        },
    [PORT_RT2880] =
        {
            .name = "Palmchip BK-3103",
            .fifo_size = PORT_SIXTEEN,
            .tx_loadsz = PORT_SIXTEEN,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
            .rxtrig_bytes = {PORT_ONE, PORT_FOUR, PORT_EIGHT, PORT_FOURTEEN},
            .flags = UART_CAP_FIFO,
        },
    [PORT_DA830] =
        {
            .name = "TI DA8xx/66AK2x",
            .fifo_size = PORT_SIXTEEN,
            .tx_loadsz = PORT_SIXTEEN,
            .fcr = UART_FCR_DMA_SELECT | UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
            .rxtrig_bytes = {PORT_ONE, PORT_FOUR, PORT_EIGHT, PORT_FOURTEEN},
            .flags = UART_CAP_FIFO | UART_CAP_AFE,
        },
    [PORT_MTK_BTIF] =
        {
            .name = "MediaTek BTIF",
            .fifo_size = PORT_SIXTEEN,
            .tx_loadsz = PORT_SIXTEEN,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
            .flags = UART_CAP_FIFO,
        },
    [PORT_NPCM] =
        {
            .name = "Nuvoton 16550",
            .fifo_size = PORT_SIXTEEN,
            .tx_loadsz = PORT_SIXTEEN,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10 | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
            .rxtrig_bytes = {PORT_ONE, PORT_FOUR, PORT_EIGHT, PORT_FOURTEEN},
            .flags = UART_CAP_FIFO,
        },
    [PORT_SUNIX] =
        {
            .name = "Sunix",
            .fifo_size = PORT_ONEHUNDREDTWENTYEIGHT,
            .tx_loadsz = PORT_ONEHUNDREDTWENTYEIGHT,
            .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
            .rxtrig_bytes = {PORT_ONE, PORT_THIRTYTWO, PORT_SIXTYFOUR, PORT_ONEHUNDREDTWELVE},
            .flags = UART_CAP_FIFO | UART_CAP_SLEEP,
        },
};

/* Uart divisor latch read */
static int default_serial_dl_read(struct uart_8250_port *up)
{
    /* Assign these in pieces to truncate any bits above 7.  */
    unsigned char dll = serial_in(up, UART_DLL);
    unsigned char dlm = serial_in(up, UART_DLM);

    return dll | (dlm << PORT_EIGHT);
}

/* Uart divisor latch write */
static void default_serial_dl_write(struct uart_8250_port *up, int value)
{
    serial_out(up, UART_DLL, value & 0xff);
    serial_out(up, UART_DLM, value >> (PORT_EIGHT & 0xff));
}

#ifdef CONFIG_SERIAL_8250_RT288X

/* Au1x00/RT288x UART hardware has a weird register layout */
static const s8 au_io_in_map[PORT_EIGHT] = {
    0,  /* UART_RX  */
    2,  /* UART_IER */
    3,  /* UART_IIR */
    5,  /* UART_LCR */
    6,  /* UART_MCR */
    7,  /* UART_LSR */
    8,  /* UART_MSR */
    -1, /* UART_SCR (unmapped) */
};

static const s8 au_io_out_map[PORT_EIGHT] = {
    1,  /* UART_TX  */
    2,  /* UART_IER */
    4,  /* UART_FCR */
    5,  /* UART_LCR */
    6,  /* UART_MCR */
    -1, /* UART_LSR (unmapped) */
    -1, /* UART_MSR (unmapped) */
    -1, /* UART_SCR (unmapped) */
};

unsigned int au_serial_in(struct uart_port *p, int offset)
{
    if (offset >= ARRAY_SIZE(au_io_in_map)) {
        return UINT_MAX;
    }
    offset = au_io_in_map[offset];
    if (offset < 0) {
        return UINT_MAX;
    }
    return __raw_readl(p->membase + (offset << p->regshift));
}

void au_serial_out(struct uart_port *p, int offset, int value)
{
    if (offset >= ARRAY_SIZE(au_io_out_map)) {
        return;
    }
    offset = au_io_out_map[offset];
    if (offset < 0) {
        return;
    }
    __raw_writel(value, p->membase + (offset << p->regshift));
}

/* Au1x00 haven't got a standard divisor latch */
static int au_serial_dl_read(struct uart_8250_port *up)
{
    return __raw_readl(up->port.membase + 0x28);
}

static void au_serial_dl_write(struct uart_8250_port *up, int value)
{
    __raw_writel(value, up->port.membase + 0x28);
}

#endif

static unsigned int hub6_serial_in(struct uart_port *p, int offset)
{
    offset = offset << p->regshift;
    outb(p->hub6 - 1 + offset, p->iobase);
    return inb(p->iobase + 1);
}

static void hub6_serial_out(struct uart_port *p, int offset, int value)
{
    offset = offset << p->regshift;
    outb(p->hub6 - 1 + offset, p->iobase);
    outb(value, p->iobase + 1);
}

static unsigned int mem_serial_in(struct uart_port *p, int offset)
{
    offset = offset << p->regshift;
    return readb(p->membase + offset);
}

static void mem_serial_out(struct uart_port *p, int offset, int value)
{
    offset = offset << p->regshift;
    writeb(value, p->membase + offset);
}

static void mem16_serial_out(struct uart_port *p, int offset, int value)
{
    offset = offset << p->regshift;
    writew(value, p->membase + offset);
}

static unsigned int mem16_serial_in(struct uart_port *p, int offset)
{
    offset = offset << p->regshift;
    return readw(p->membase + offset);
}

static void mem32_serial_out(struct uart_port *p, int offset, int value)
{
    offset = offset << p->regshift;
    writel(value, p->membase + offset);
}

static unsigned int mem32_serial_in(struct uart_port *p, int offset)
{
    offset = offset << p->regshift;
    return readl(p->membase + offset);
}

static void mem32be_serial_out(struct uart_port *p, int offset, int value)
{
    offset = offset << p->regshift;
    iowrite32be(value, p->membase + offset);
}

static unsigned int mem32be_serial_in(struct uart_port *p, int offset)
{
    offset = offset << p->regshift;
    return ioread32be(p->membase + offset);
}

static unsigned int io_serial_in(struct uart_port *p, int offset)
{
    offset = offset << p->regshift;
    return inb(p->iobase + offset);
}

static void io_serial_out(struct uart_port *p, int offset, int value)
{
    offset = offset << p->regshift;
    outb(value, p->iobase + offset);
}

static int serial8250_default_handle_irq(struct uart_port *port);

static void set_io_from_upio(struct uart_port *p)
{
    struct uart_8250_port *up = up_to_u8250p(p);

    up->dl_read = default_serial_dl_read;
    up->dl_write = default_serial_dl_write;

    switch (p->iotype) {
        case UPIO_HUB6:
            p->serial_in = hub6_serial_in;
            p->serial_out = hub6_serial_out;
            break;

        case UPIO_MEM:
            p->serial_in = mem_serial_in;
            p->serial_out = mem_serial_out;
            break;

        case UPIO_MEM16:
            p->serial_in = mem16_serial_in;
            p->serial_out = mem16_serial_out;
            break;

        case UPIO_MEM32:
            p->serial_in = mem32_serial_in;
            p->serial_out = mem32_serial_out;
            break;

        case UPIO_MEM32BE:
            p->serial_in = mem32be_serial_in;
            p->serial_out = mem32be_serial_out;
            break;

#ifdef CONFIG_SERIAL_8250_RT288X
        case UPIO_AU:
            p->serial_in = au_serial_in;
            p->serial_out = au_serial_out;
            up->dl_read = au_serial_dl_read;
            up->dl_write = au_serial_dl_write;
            break;
#endif

        default:
            p->serial_in = io_serial_in;
            p->serial_out = io_serial_out;
            break;
    }
    /* Remember loaded iotype */
    up->cur_iotype = p->iotype;
    p->handle_irq = serial8250_default_handle_irq;
}

static void serial_port_out_sync(struct uart_port *p, int offset, int value)
{
    switch (p->iotype) {
        case UPIO_MEM:
        case UPIO_MEM16:
        case UPIO_MEM32:
        case UPIO_MEM32BE:
        case UPIO_AU:
            p->serial_out(p, offset, value);
            p->serial_in(p, UART_LCR); /* safe, no side-effects */
            break;
        default:
            p->serial_out(p, offset, value);
    }
}


/*
 * FIFO support.
 */
static void serial8250_clear_fifos(struct uart_8250_port *p)
{
    if (p->capabilities & UART_CAP_FIFO) {
        serial_out(p, UART_FCR, UART_FCR_ENABLE_FIFO);
        serial_out(p, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
        serial_out(p, UART_FCR, 0);
    }
}

static enum hrtimer_restart serial8250_em485_handle_start_tx(struct hrtimer *t);
static enum hrtimer_restart serial8250_em485_handle_stop_tx(struct hrtimer *t);

void serial8250_clear_and_reinit_fifos(struct uart_8250_port *p)
{
    serial8250_clear_fifos(p);
    serial_out(p, UART_FCR, p->fcr);
}
EXPORT_SYMBOL_GPL(serial8250_clear_and_reinit_fifos);

void serial8250_rpm_get(struct uart_8250_port *p)
{
    if (!(p->capabilities & UART_CAP_RPM)) {
        return;
    }
    pm_runtime_get_sync(p->port.dev);
}
EXPORT_SYMBOL_GPL(serial8250_rpm_get);

void serial8250_rpm_put(struct uart_8250_port *p)
{
    if (!(p->capabilities & UART_CAP_RPM)) {
        return;
    }
    pm_runtime_mark_last_busy(p->port.dev);
    pm_runtime_put_autosuspend(p->port.dev);
}
EXPORT_SYMBOL_GPL(serial8250_rpm_put);

/**
 *    serial8250_em485_init() - put uart_8250_port into rs485 emulating
 *    @p:    uart_8250_port port instance
 *
 *    The function is used to start rs485 software emulating on the
 *    &struct uart_8250_port* @p. Namely, RTS is switched before/after
 *    transmission. The function is idempotent, so it is safe to call it
 *    multiple times.
 *
 *    The caller MUST enable interrupt on empty shift register before
 *    calling serial8250_em485_init(). This interrupt is not a part of
 *    8250 standard, but implementation defined.
 *
 *    The function is supposed to be called from .rs485_config callback
 *    or from any other callback protected with p->port.lock spinlock.
 *
 *    See also serial8250_em485_destroy()
 *
 *    Return 0 - success, -errno - otherwise
 */
static int serial8250_em485_init(struct uart_8250_port *p)
{
    if (p->em485) {
        return 0;
    }

    p->em485 = kmalloc(sizeof(struct uart_8250_em485), GFP_ATOMIC);
    if (!p->em485) {
        return -ENOMEM;
    }

    hrtimer_init(&p->em485->stop_tx_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    hrtimer_init(&p->em485->start_tx_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    p->em485->stop_tx_timer.function = &serial8250_em485_handle_stop_tx;
    p->em485->start_tx_timer.function = &serial8250_em485_handle_start_tx;
    p->em485->port = p;
    p->em485->active_timer = NULL;
    p->em485->tx_stopped = true;

    p->rs485_stop_tx(p);

    return 0;
}

/**
 *    serial8250_em485_destroy() - put uart_8250_port into normal state
 *    @p:    uart_8250_port port instance
 *
 *    The function is used to stop rs485 software emulating on the
 *    &struct uart_8250_port* @p. The function is idempotent, so it is safe to
 *    call it multiple times.
 *
 *    The function is supposed to be called from .rs485_config callback
 *    or from any other callback protected with p->port.lock spinlock.
 *
 *    See also serial8250_em485_init()
 */
void serial8250_em485_destroy(struct uart_8250_port *p)
{
    if (!p->em485) {
        return;
    }

    hrtimer_cancel(&p->em485->start_tx_timer);
    hrtimer_cancel(&p->em485->stop_tx_timer);

    kfree(p->em485);
    p->em485 = NULL;
}
EXPORT_SYMBOL_GPL(serial8250_em485_destroy);

/**
 * serial8250_em485_config() - generic ->rs485_config() callback
 * @port: uart port
 * @rs485: rs485 settings
 *
 * Generic callback usable by 8250 uart drivers to activate rs485 settings
 * if the uart is incapable of driving RTS as a Transmit Enable signal in
 * hardware, relying on software emulation instead.
 */
int serial8250_em485_config(struct uart_port *port, struct serial_rs485 *rs485)
{
    struct uart_8250_port *up = up_to_u8250p(port);

    /* pick sane settings if the user hasn't */
    if (!!(rs485->flags & SER_RS485_RTS_ON_SEND) == !!(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
        rs485->flags |= SER_RS485_RTS_ON_SEND;
        rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
    }

    /* clamp the delays to [0, 100ms] */
    rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U);
    rs485->delay_rts_after_send = min(rs485->delay_rts_after_send, 100U);

    memset(rs485->padding, 0, sizeof(rs485->padding));
    port->rs485 = *rs485;

    gpiod_set_value(port->rs485_term_gpio, rs485->flags & SER_RS485_TERMINATE_BUS);

    /*
     * Both serial8250_em485_init() and serial8250_em485_destroy()
     * are idempotent.
     */
    if (rs485->flags & SER_RS485_ENABLED) {
        int ret = serial8250_em485_init(up);
        if (ret) {
            rs485->flags &= ~SER_RS485_ENABLED;
            port->rs485.flags &= ~SER_RS485_ENABLED;
        }
        return ret;
    }

    serial8250_em485_destroy(up);
    return 0;
}
EXPORT_SYMBOL_GPL(serial8250_em485_config);

/*
 * These two wrappers ensure that enable_runtime_pm_tx() can be called more than
 * once and disable_runtime_pm_tx() will still disable RPM because the fifo is
 * empty and the HW can idle again.
 */
void serial8250_rpm_get_tx(struct uart_8250_port *p)
{
    unsigned char rpm_active;

    if (!(p->capabilities & UART_CAP_RPM)) {
        return;
    }

    rpm_active = xchg(&p->rpm_tx_active, 1);
    if (rpm_active) {
        return;
    }
    pm_runtime_get_sync(p->port.dev);
}
EXPORT_SYMBOL_GPL(serial8250_rpm_get_tx);

void serial8250_rpm_put_tx(struct uart_8250_port *p)
{
    unsigned char rpm_active;

    if (!(p->capabilities & UART_CAP_RPM)) {
        return;
    }

    rpm_active = xchg(&p->rpm_tx_active, 0);
    if (!rpm_active) {
        return;
    }
    pm_runtime_mark_last_busy(p->port.dev);
    pm_runtime_put_autosuspend(p->port.dev);
}
EXPORT_SYMBOL_GPL(serial8250_rpm_put_tx);

/*
 * IER sleep support.  UARTs which have EFRs need the "extended
 * capability" bit enabled.  Note that on XR16C850s, we need to
 * reset LCR to write to IER.
 */
static void serial8250_set_sleep(struct uart_8250_port *p, int sleep)
{
    unsigned char lcr = 0, efr = 0;

    serial8250_rpm_get(p);

    if (p->capabilities & UART_CAP_SLEEP) {
        if (p->capabilities & UART_CAP_EFR) {
            lcr = serial_in(p, UART_LCR);
            efr = serial_in(p, UART_EFR);
            serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B);
            serial_out(p, UART_EFR, UART_EFR_ECB);
            serial_out(p, UART_LCR, 0);
        }
        serial_out(p, UART_IER, sleep ? UART_IERX_SLEEP : 0);
        if (p->capabilities & UART_CAP_EFR) {
            serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B);
            serial_out(p, UART_EFR, efr);
            serial_out(p, UART_LCR, lcr);
        }
    }

    serial8250_rpm_put(p);
}

#ifdef CONFIG_SERIAL_8250_RSA
/*
 * Attempts to turn on the RSA FIFO.  Returns zero on failure.
 * We set the port uart clock rate if we succeed.
 */
static int __enable_rsa(struct uart_8250_port *up)
{
    unsigned char mode;
    int result;

    mode = serial_in(up, UART_RSA_MSR);
    result = mode & UART_RSA_MSR_FIFO;

    if (!result) {
        serial_out(up, UART_RSA_MSR, mode | UART_RSA_MSR_FIFO);
        mode = serial_in(up, UART_RSA_MSR);
        result = mode & UART_RSA_MSR_FIFO;
    }

    if (result) {
        up->port.uartclk = SERIAL_RSA_BAUD_BASE * PORT_SIXTEEN;
    }

    return result;
}

static void enable_rsa(struct uart_8250_port *up)
{
    if (up->port.type == PORT_RSA) {
        if (up->port.uartclk != SERIAL_RSA_BAUD_BASE * PORT_SIXTEEN) {
            spin_lock_irq(&up->port.lock);
            __enable_rsa(up);
            spin_unlock_irq(&up->port.lock);
        }
        if (up->port.uartclk == SERIAL_RSA_BAUD_BASE * PORT_SIXTEEN) {
            serial_out(up, UART_RSA_FRR, 0);
        }
    }
}

/*
 * Attempts to turn off the RSA FIFO.  Returns zero on failure.
 * It is unknown why interrupts were disabled in here.  However,
 * the caller is expected to preserve this behaviour by grabbing
 * the spinlock before calling this function.
 */
static void disable_rsa(struct uart_8250_port *up)
{
    unsigned char mode;
    int result;

    if (up->port.type == PORT_RSA && up->port.uartclk == SERIAL_RSA_BAUD_BASE * PORT_SIXTEEN) {
        spin_lock_irq(&up->port.lock);

        mode = serial_in(up, UART_RSA_MSR);
        result = !(mode & UART_RSA_MSR_FIFO);

        if (!result) {
            serial_out(up, UART_RSA_MSR, mode & ~UART_RSA_MSR_FIFO);
            mode = serial_in(up, UART_RSA_MSR);
            result = !(mode & UART_RSA_MSR_FIFO);
        }

        if (result) {
            up->port.uartclk = SERIAL_RSA_BAUD_BASE_LO * PORT_SIXTEEN;
        }
        spin_unlock_irq(&up->port.lock);
    }
}
#endif /* CONFIG_SERIAL_8250_RSA */

/*
 * This is a quickie test to see how big the FIFO is.
 * It doesn't work at all the time, more's the pity.
 */
static int size_fifo(struct uart_8250_port *up)
{
    unsigned char old_fcr, old_mcr, old_lcr;
    unsigned short old_dl;
    int count;

    old_lcr = serial_in(up, UART_LCR);
    serial_out(up, UART_LCR, 0);
    old_fcr = serial_in(up, UART_FCR);
    old_mcr = serial8250_in_MCR(up);
    serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
    serial8250_out_MCR(up, UART_MCR_LOOP);
    serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
    old_dl = serial_dl_read(up);
    serial_dl_write(up, 0x0001);
    serial_out(up, UART_LCR, 0x03);
    for (count = 0; count < PORT_ONEHUNDREDFIFTYSIX; count++) {
        serial_out(up, UART_TX, count);
    }
    mdelay(0x14); /* schedule_timeout */
    for (count = 0; (serial_in(up, UART_LSR) & UART_LSR_DR) && (count < PORT_ONEHUNDREDFIFTYSIX); count++) {
        serial_in(up, UART_RX);
    }
    serial_out(up, UART_FCR, old_fcr);
    serial8250_out_MCR(up, old_mcr);
    serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
    serial_dl_write(up, old_dl);
    serial_out(up, UART_LCR, old_lcr);

    return count;
}

/*
 * Read UART ID using the divisor method - set DLL and DLM to zero
 * and the revision will be in DLL and device type in DLM.  We
 * preserve the device state across this.
 */
static unsigned int autoconfig_read_divisor_id(struct uart_8250_port *p)
{
    unsigned char old_lcr;
    unsigned int id, old_dl;

    old_lcr = serial_in(p, UART_LCR);
    serial_out(p, UART_LCR, UART_LCR_CONF_MODE_A);
    old_dl = serial_dl_read(p);
    serial_dl_write(p, 0);
    id = serial_dl_read(p);
    serial_dl_write(p, old_dl);

    serial_out(p, UART_LCR, old_lcr);

    return id;
}

/*
 * This is a helper routine to autodetect StarTech/Exar/Oxsemi UART's.
 * When this function is called we know it is at least a StarTech
 * 16650 V2, but it might be one of several StarTech UARTs, or one of
 * its clones.  (We treat the broken original StarTech 16650 V1 as a
 * 16550, and why not?  Startech doesn't seem to even acknowledge its
 * existence.)
 *
 * What evil have men's minds wrought...
 */
static void autoconfig_has_efr(struct uart_8250_port *up)
{
    unsigned int id1, id2, id3, rev;

    /*
     * Everything with an EFR has SLEEP
     */
    up->capabilities |= UART_CAP_EFR | UART_CAP_SLEEP;

    /*
     * First we check to see if it's an Oxford Semiconductor UART.
     *
     * If we have to do this here because some non-National
     * Semiconductor clone chips lock up if you try writing to the
     * LSR register (which serial_icr_read does)
     */

    /*
     * Check for Oxford Semiconductor 16C950.
     *
     * EFR [4] must be set else this test fails.
     *
     * This shouldn't be necessary, but Mike Hudson (Exoray@isys.ca)
     * claims that it's needed for 952 dual UART's (which are not
     * recommended for new designs).
     */
    up->acr = 0;
    serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
    serial_out(up, UART_EFR, UART_EFR_ECB);
    serial_out(up, UART_LCR, 0x00);
    id1 = serial_icr_read(up, UART_ID1);
    id2 = serial_icr_read(up, UART_ID2);
    id3 = serial_icr_read(up, UART_ID3);
    rev = serial_icr_read(up, UART_REV);

    DEBUG_AUTOCONF("950id=%02x:%02x:%02x:%02x ", id1, id2, id3, rev);

    if (id1 == 0x16 && id2 == 0xC9 && (id3 == 0x50 || id3 == 0x52 || id3 == 0x54)) {
        up->port.type = PORT_16C950;

        /*
         * Enable work around for the Oxford Semiconductor 952 rev B
         * chip which causes it to seriously miscalculate baud rates
         * when DLL is 0.
         */
        if (id3 == 0x52 && rev == 0x01) {
            up->bugs |= UART_BUG_QUOT;
        }
        return;
    }

    /*
     * We check for a XR16C850 by setting DLL and DLM to 0, and then
     * reading back DLL and DLM.  The chip type depends on the DLM
     * value read back:
     *  0x10 - XR16C850 and the DLL contains the chip revision.
     *  0x12 - XR16C2850.
     *  0x14 - XR16C854.
     */
    id1 = autoconfig_read_divisor_id(up);
    DEBUG_AUTOCONF("850id=%04x ", id1);

    id2 = id1 >> 0x8;
    if (id2 == 0x10 || id2 == 0x12 || id2 == 0x14) {
        up->port.type = PORT_16850;
        return;
    }

    /*
     * It wasn't an XR16C850.
     *
     * We distinguish between the '654 and the '650 by counting
     * how many bytes are in the FIFO.  I'm using this for now,
     * since that's the technique that was sent to me in the
     * serial driver update, but I'm not convinced this works.
     * I've had problems doing this in the past.  -TYT
     */
    if (size_fifo(up) == PORT_SIXTYFOUR) {
        up->port.type = PORT_16654;
    } else {
        up->port.type = PORT_16650V2;
    }
}

/*
 * We detected a chip without a FIFO.  Only two fall into
 * this category - the original 8250 and the 16450.  The
 * 16450 has a scratch register (accessible with LCR=0)
 */
static void autoconfig_8250(struct uart_8250_port *up)
{
    unsigned char scratch, status1, status2;

    up->port.type = PORT_8250;

    scratch = serial_in(up, UART_SCR);
    serial_out(up, UART_SCR, 0xa5);
    status1 = serial_in(up, UART_SCR);
    serial_out(up, UART_SCR, 0x5a);
    status2 = serial_in(up, UART_SCR);
    serial_out(up, UART_SCR, scratch);

    if (status1 == 0xa5 && status2 == 0x5a) {
        up->port.type = PORT_16450;
    }
}

static int broken_efr(struct uart_8250_port *up)
{
    /*
     * Exar ST16C2550 "A2" devices incorrectly detect as
     * having an EFR, and report an ID of 0x0201.  See
     * http://linux.derkeiler.com/Mailing-Lists/Kernel/2004-11/4812.html
     */
    if (autoconfig_read_divisor_id(up) == 0x0201 && size_fifo(up) == PORT_SIXTEEN) {
        return 1;
    }

    return 0;
}

/*
 * We know that the chip has FIFOs.  Does it have an EFR?  The
 * EFR is located in the same register position as the IIR and
 * we know the top two bits of the IIR are currently set.  The
 * EFR should contain zero.  Try to read the EFR.
 */
static void autoconfig_16550a(struct uart_8250_port *up)
{
    unsigned char status1, status2;
    unsigned int iersave;

    up->port.type = PORT_16550A;
    up->capabilities |= UART_CAP_FIFO;

    if (!IS_ENABLED(CONFIG_SERIAL_8250_16550A_VARIANTS)) {
        return;
    }

    /*
     * Check for presence of the EFR when DLAB is set.
     * Only ST16C650V1 UARTs pass this test.
     */
    serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
    if (serial_in(up, UART_EFR) == 0) {
        serial_out(up, UART_EFR, 0xA8);
        if (serial_in(up, UART_EFR) != 0) {
            DEBUG_AUTOCONF("EFRv1 ");
            up->port.type = PORT_16650;
            up->capabilities |= UART_CAP_EFR | UART_CAP_SLEEP;
        } else {
            serial_out(up, UART_LCR, 0);
            serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR7_64BYTE);
            status1 = serial_in(up, UART_IIR) >> 0x5;
            serial_out(up, UART_FCR, 0);
            serial_out(up, UART_LCR, 0);

            if (status1 == PORT_SEVEN) {
                up->port.type = PORT_16550A_FSL64;
            } else {
                DEBUG_AUTOCONF("Motorola 8xxx DUART ");
            }
        }
        serial_out(up, UART_EFR, 0);
        return;
    }

    /*
     * Maybe it requires 0xbf to be written to the LCR.
     * (other ST16C650V2 UARTs, TI16C752A, etc)
     */
    serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
    if (serial_in(up, UART_EFR) == 0 && !broken_efr(up)) {
        DEBUG_AUTOCONF("EFRv2 ");
        autoconfig_has_efr(up);
        return;
    }

    /*
     * Check for a National Semiconductor SuperIO chip.
     * Attempt to switch to bank 2, read the value of the LOOP bit
     * from EXCR1. Switch back to bank 0, change it in MCR. Then
     * switch back to bank 2, read it from EXCR1 again and check
     * it's changed. If so, set baud_base in EXCR2 to 921600. -- dwmw2
     */
    serial_out(up, UART_LCR, 0);
    status1 = serial8250_in_MCR(up);
    serial_out(up, UART_LCR, 0xE0);
    status2 = serial_in(up, 0x02); /* EXCR1 */
    if (!((status2 ^ status1) & UART_MCR_LOOP)) {
        serial_out(up, UART_LCR, 0);
        serial8250_out_MCR(up, status1 ^ UART_MCR_LOOP);
        serial_out(up, UART_LCR, 0xE0);
        status2 = serial_in(up, 0x02); /* EXCR1 */
        serial_out(up, UART_LCR, 0);
        serial8250_out_MCR(up, status1);

        if ((status2 ^ status1) & UART_MCR_LOOP) {
            unsigned short quot;

            serial_out(up, UART_LCR, 0xE0);

            quot = serial_dl_read(up);
            quot <<= 0x3;

            if (ns16550a_goto_highspeed(up)) {
                serial_dl_write(up, quot);
            }

            serial_out(up, UART_LCR, 0);

            up->port.uartclk = 0xe1000 * 0x10;
            up->port.type = PORT_NS16550A;
            up->capabilities |= UART_NATSEMI;
            return;
        }
    }

    /*
     * No EFR.  Try to detect a TI16750, which only sets bit 5 of
     * the IIR when 64 byte FIFO mode is enabled when DLAB is set.
     * Try setting it with and without DLAB set.  Cheap clones
     * set bit 5 without DLAB set.
     */
    serial_out(up, UART_LCR, 0);
    serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR7_64BYTE);
    status1 = serial_in(up, UART_IIR) >> PORT_FIVE;
    serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO);
    serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
    serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR7_64BYTE);
    status2 = serial_in(up, UART_IIR) >> PORT_FIVE;
    serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO);
    serial_out(up, UART_LCR, 0);

    DEBUG_AUTOCONF("iir1=%d iir2=%d ", status1, status2);

    if (status1 == PORT_SIX && status2 == PORT_SEVEN) {
        up->port.type = PORT_16750;
        up->capabilities |= UART_CAP_AFE | UART_CAP_SLEEP;
        return;
    }

    /*
     * Try writing and reading the UART_IER_UUE bit (b6).
     * If it works, this is probably one of the Xscale platform's
     * internal UARTs.
     * We're going to explicitly set the UUE bit to 0 before
     * trying to write and read a 1 just to make sure it's not
     * already a 1 and maybe locked there before we even start start.
     */
    iersave = serial_in(up, UART_IER);
    serial_out(up, UART_IER, iersave & ~UART_IER_UUE);
    if (!(serial_in(up, UART_IER) & UART_IER_UUE)) {
        /*
         * OK it's in a known zero state, try writing and reading
         * without disturbing the current state of the other bits.
         */
        serial_out(up, UART_IER, iersave | UART_IER_UUE);
        if (serial_in(up, UART_IER) & UART_IER_UUE) {
            /*
             * It's an Xscale.
             * We'll leave the UART_IER_UUE bit set to 1 (enabled).
             */
            DEBUG_AUTOCONF("Xscale ");
            up->port.type = PORT_XSCALE;
            up->capabilities |= UART_CAP_UUE | UART_CAP_RTOIE;
            return;
        }
    } else {
        /*
         * If we got here we couldn't force the IER_UUE bit to 0.
         * Log it and continue.
         */
        DEBUG_AUTOCONF("Couldn't force IER_UUE to 0 ");
    }
    serial_out(up, UART_IER, iersave);

    /*
     * We distinguish between 16550A and U6 16550A by counting
     * how many bytes are in the FIFO.
     */
    if (up->port.type == PORT_16550A && size_fifo(up) == PORT_SIXTYFOUR) {
        up->port.type = PORT_U6_16550A;
        up->capabilities |= UART_CAP_AFE;
    }
}

/*
 * This routine is called by rs_init() to initialize a specific serial
 * port.  It determines what type of UART chip this serial port is
 * using: 8250, 16450, 16550, 16550A.  The important question is
 * whether or not this UART is a 16550A or not, since this will
 * determine whether or not we can use its FIFO features or not.
 */
static void autoconfig(struct uart_8250_port *up)
{
    unsigned char status1, scratch, scratch2, scratch3;
    unsigned char save_lcr, save_mcr;
    struct uart_port *port = &up->port;
    unsigned long flags;
    unsigned int old_capabilities;

    if (!port->iobase && !port->mapbase && !port->membase) {
        return;
    }

    DEBUG_AUTOCONF("%s: autoconf (0x%04lx, 0x%p): ", port->name, port->iobase, port->membase);

    /*
     * We really do need global IRQs disabled here - we're going to
     * be frobbing the chips IRQ enable register to see if it exists.
     */
    spin_lock_irqsave(&port->lock, flags);

    up->capabilities = 0;
    up->bugs = 0;

    if (!(port->flags & UPF_BUGGY_UART)) {
        /*
         * Do a simple existence test first; if we fail this,
         * there's no point trying anything else.
         *
         * 0x80 is used as a nonsense port to prevent against
         * false positives due to ISA bus float.  The
         * assumption is that 0x80 is a non-existent port;
         * which should be safe since include/asm/io.h also
         * makes this assumption.
         *
         * Note: this is safe as long as MCR bit 4 is clear
         * and the device is in "PC" mode.
         */
        scratch = serial_in(up, UART_IER);
        serial_out(up, UART_IER, 0);
#ifdef __i386__
        outb(0xff, 0x080);
#endif
        /*
         * Mask out IER[7:4] bits for test as some UARTs (e.g. TL
         * 16C754B) allow only to modify them if an EFR bit is set.
         */
        scratch2 = serial_in(up, UART_IER) & 0x0f;
        serial_out(up, UART_IER, 0x0F);
#ifdef __i386__
        outb(0, 0x080);
#endif
        scratch3 = serial_in(up, UART_IER) & 0x0f;
        serial_out(up, UART_IER, scratch);
        if (scratch2 != 0 || scratch3 != 0x0F) {
            /*
             * We failed; there's nothing here
             */
            spin_unlock_irqrestore(&port->lock, flags);
            DEBUG_AUTOCONF("IER test failed (%02x, %02x) ", scratch2, scratch3);
            goto out;
        }
    }

    save_mcr = serial8250_in_MCR(up);
    save_lcr = serial_in(up, UART_LCR);

    /*
     * Check to see if a UART is really there.  Certain broken
     * internal modems based on the Rockwell chipset fail this
     * test, because they apparently don't implement the loopback
     * test mode.  So this test is skipped on the COM 1 through
     * COM 4 ports.  This *should* be safe, since no board
     * manufacturer would be stupid enough to design a board
     * that conflicts with COM 1-4 --- we hope!
     */
    if (!(port->flags & UPF_SKIP_TEST)) {
        serial8250_out_MCR(up, UART_MCR_LOOP | 0x0A);
        status1 = serial_in(up, UART_MSR) & 0xF0;
        serial8250_out_MCR(up, save_mcr);
        if (status1 != 0x90) {
            spin_unlock_irqrestore(&port->lock, flags);
            DEBUG_AUTOCONF("LOOP test failed (%02x) ", status1);
            goto out;
        }
    }

    /*
     * We're pretty sure there's a port here.  Lets find out what
     * type of port it is.  The IIR top two bits allows us to find
     * out if it's 8250 or 16450, 16550, 16550A or later.  This
     * determines what we test for next.
     *
     * We also initialise the EFR (if any) to zero for later.  The
     * EFR occupies the same register location as the FCR and IIR.
     */
    serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
    serial_out(up, UART_EFR, 0);
    serial_out(up, UART_LCR, 0);

    serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO);

    /* Assign this as it is to truncate any bits above 7.  */
    scratch = serial_in(up, UART_IIR);

    switch (scratch >> 0x6) {
        case 0x0:
            autoconfig_8250(up);
            break;
        case 0x1:
            port->type = PORT_UNKNOWN;
            break;
        case 0x2:
            port->type = PORT_16550;
            break;
        case 0x3:
            autoconfig_16550a(up);
            break;
        default:
            break;
    }

#ifdef CONFIG_SERIAL_8250_RSA
    /*
     * Only probe for RSA ports if we got the region.
     */
    if ((port->type == PORT_16550A) && (up->probe & UART_PROBE_RSA) && __enable_rsa(up)) {
        port->type = PORT_RSA;
    }
#endif

    serial_out(up, UART_LCR, save_lcr);

    port->fifosize = uart_config[up->port.type].fifo_size;
    old_capabilities = up->capabilities;
    up->capabilities = uart_config[port->type].flags;
    up->tx_loadsz = uart_config[port->type].tx_loadsz;

    if (port->type == PORT_UNKNOWN) {
        goto out_lock;
    }

    /*
     * Reset the UART.
     */
#ifdef CONFIG_SERIAL_8250_RSA
    if (port->type == PORT_RSA) {
        serial_out(up, UART_RSA_FRR, 0);
    }
#endif
    serial8250_out_MCR(up, save_mcr);
    serial8250_clear_fifos(up);
    serial_in(up, UART_RX);
    if (up->capabilities & UART_CAP_UUE) {
        serial_out(up, UART_IER, UART_IER_UUE);
    } else {
        serial_out(up, UART_IER, 0);
    }

out_lock:
    spin_unlock_irqrestore(&port->lock, flags);

    /*
     * Check if the device is a Fintek F81216A
     */
    if (port->type == PORT_16550A && port->iotype == UPIO_PORT) {
        fintek_8250_probe(up);
    }

    if (up->capabilities != old_capabilities) {
        dev_warn(port->dev, "detected caps %08x should be %08x\n", old_capabilities, up->capabilities);
    }
out:
    DEBUG_AUTOCONF("iir=%d ", scratch);
    DEBUG_AUTOCONF("type=%s\n", uart_config[port->type].name);
}

static void autoconfig_irq(struct uart_8250_port *up)
{
    struct uart_port *port = &up->port;
    unsigned char save_mcr, save_ier;
    unsigned char save_ICP = 0;
    unsigned int ICP = 0;
    unsigned long irqs;
    int irq;

    if (port->flags & UPF_FOURPORT) {
        ICP = (port->iobase & 0xfe0) | 0x1f;
        save_ICP = inb_p(ICP);
        outb_p(0x80, ICP);
        inb_p(ICP);
    }

    if (uart_console(port)) {
        console_lock();
    }

    /* forget possible initially masked and pending IRQ */
    probe_irq_off(probe_irq_on());
    save_mcr = serial8250_in_MCR(up);
    save_ier = serial_in(up, UART_IER);
    serial8250_out_MCR(up, UART_MCR_OUT1 | UART_MCR_OUT2);

    irqs = probe_irq_on();
    serial8250_out_MCR(up, 0);
    udelay(0xa);
    if (port->flags & UPF_FOURPORT) {
        serial8250_out_MCR(up, UART_MCR_DTR | UART_MCR_RTS);
    } else {
        serial8250_out_MCR(up, UART_MCR_DTR | UART_MCR_RTS | UART_MCR_OUT2);
    }
    serial_out(up, UART_IER, 0x0f); /* enable all intrs */
    serial_in(up, UART_LSR);
    serial_in(up, UART_RX);
    serial_in(up, UART_IIR);
    serial_in(up, UART_MSR);
    serial_out(up, UART_TX, 0xFF);
    udelay(0x14);
    irq = probe_irq_off(irqs);

    serial8250_out_MCR(up, save_mcr);
    serial_out(up, UART_IER, save_ier);

    if (port->flags & UPF_FOURPORT) {
        outb_p(save_ICP, ICP);
    }

    if (uart_console(port)) {
        console_unlock();
    }

    port->irq = (irq > 0) ? irq : 0;
}

static void serial8250_stop_rx(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);

    serial8250_rpm_get(up);

    up->ier &= ~(UART_IER_RLSI | UART_IER_RDI);
    up->port.read_status_mask &= ~UART_LSR_DR;
    serial_port_out(port, UART_IER, up->ier);

    serial8250_rpm_put(up);
}

/**
 * serial8250_em485_stop_tx() - generic ->rs485_stop_tx() callback
 * @p: uart 8250 port
 *
 * Generic callback usable by 8250 uart drivers to stop rs485 transmission.
 */
void serial8250_em485_stop_tx(struct uart_8250_port *p)
{
    unsigned char mcr = serial8250_in_MCR(p);

    if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) {
        mcr |= UART_MCR_RTS;
    } else {
        mcr &= ~UART_MCR_RTS;
    }
    serial8250_out_MCR(p, mcr);

    /*
     * Empty the RX FIFO, we are not interested in anything
     * received during the half-duplex transmission.
     * Enable previously disabled RX interrupts.
     */
    if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
        serial8250_clear_and_reinit_fifos(p);

        p->ier |= UART_IER_RLSI | UART_IER_RDI;
        serial_port_out(&p->port, UART_IER, p->ier);
    }
}
EXPORT_SYMBOL_GPL(serial8250_em485_stop_tx);

static enum hrtimer_restart serial8250_em485_handle_stop_tx(struct hrtimer *t)
{
    struct uart_8250_em485 *em485;
    struct uart_8250_port *p;
    unsigned long flags;

    em485 = container_of(t, struct uart_8250_em485, stop_tx_timer);
    p = em485->port;

    serial8250_rpm_get(p);
    spin_lock_irqsave(&p->port.lock, flags);
    if (em485->active_timer == &em485->stop_tx_timer) {
        p->rs485_stop_tx(p);
        em485->active_timer = NULL;
        em485->tx_stopped = true;
    }
    spin_unlock_irqrestore(&p->port.lock, flags);
    serial8250_rpm_put(p);
    return HRTIMER_NORESTART;
}

static void start_hrtimer_ms(struct hrtimer *hrt, unsigned long msec)
{
    long sec = msec / PORT_ONETHOUSAND;
    long nsec = (msec % PORT_ONETHOUSAND) * PORT_ONETHOUSANDTHOUSAND;
    ktime_t t = ktime_set(sec, nsec);

    hrtimer_start(hrt, t, HRTIMER_MODE_REL);
}

static void __stop_tx_rs485(struct uart_8250_port *p)
{
    struct uart_8250_em485 *em485 = p->em485;

    /*
     * rs485_stop_tx() is going to set RTS according to config
     * AND flush RX FIFO if required.
     */
    if (p->port.rs485.delay_rts_after_send > 0) {
        em485->active_timer = &em485->stop_tx_timer;
        start_hrtimer_ms(&em485->stop_tx_timer, p->port.rs485.delay_rts_after_send);
    } else {
        p->rs485_stop_tx(p);
        em485->active_timer = NULL;
        em485->tx_stopped = true;
    }
}

static inline void __do_stop_tx(struct uart_8250_port *p)
{
    if (serial8250_clear_THRI(p)) {
        serial8250_rpm_put_tx(p);
    }
}

static inline void __stop_tx(struct uart_8250_port *p)
{
    struct uart_8250_em485 *em485 = p->em485;

    if (em485) {
        unsigned char lsr = serial_in(p, UART_LSR);
        p->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
        /*
         * To provide required timeing and allow FIFO transfer,
         * __stop_tx_rs485() must be called only when both FIFO and
         * shift register are empty. It is for device driver to enable
         * interrupt on TEMT.
         */
        if ((lsr & BOTH_EMPTY) != BOTH_EMPTY) {
            return;
        }

        __stop_tx_rs485(p);
    }
    __do_stop_tx(p);
}

static void serial8250_stop_tx(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);

    serial8250_rpm_get(up);
    __stop_tx(up);

    /*
     * We really want to stop the transmitter from sending.
     */
    if (port->type == PORT_16C950) {
        up->acr |= UART_ACR_TXDIS;
        serial_icr_write(up, UART_ACR, up->acr);
    }
    serial8250_rpm_put(up);
}

static inline void __start_tx(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);

#ifdef CONFIG_ARCH_ROCKCHIP
    if (up->dma && up->dma->txchan && !up->dma->tx_dma(up)) {
        return;
    }
#else
    if (up->dma && !up->dma->tx_dma(up)) {
        return;
    }
#endif

    if (serial8250_set_THRI(up)) {
        if (up->bugs & UART_BUG_TXEN) {
            unsigned char lsr;

            lsr = serial_in(up, UART_LSR);
            up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
            if (lsr & UART_LSR_THRE) {
                serial8250_tx_chars(up);
            }
        }
    }

    /*
     * Re-enable the transmitter if we disabled it.
     */
    if ((port->type == PORT_16C950) && (up->acr & UART_ACR_TXDIS)) {
        up->acr &= ~UART_ACR_TXDIS;
        serial_icr_write(up, UART_ACR, up->acr);
    }
}

/**
 * serial8250_em485_start_tx() - generic ->rs485_start_tx() callback
 * @up: uart 8250 port
 *
 * Generic callback usable by 8250 uart drivers to start rs485 transmission.
 * Assumes that setting the RTS bit in the MCR register means RTS is high.
 * (Some chips use inverse semantics.)  Further assumes that reception is
 * stoppable by disabling the UART_IER_RDI interrupt.  (Some chips set the
 * UART_LSR_DR bit even when UART_IER_RDI is disabled, foiling this approach.)
 */
void serial8250_em485_start_tx(struct uart_8250_port *p)
{
    unsigned char mcr = serial8250_in_MCR(p);

    if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
        serial8250_stop_rx(&p->port);
    }

    if (p->port.rs485.flags & SER_RS485_RTS_ON_SEND) {
        mcr |= UART_MCR_RTS;
    } else {
        mcr &= ~UART_MCR_RTS;
    }
    serial8250_out_MCR(p, mcr);
}
EXPORT_SYMBOL_GPL(serial8250_em485_start_tx);

static inline void start_tx_rs485(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    struct uart_8250_em485 *em485 = up->em485;
    /*
     * While serial8250_em485_handle_stop_tx() is a noop if
     * em485->active_timer != &em485->stop_tx_timer, it might happen that
     * the timer is still armed and triggers only after the current bunch of
     * chars is send and em485->active_timer == &em485->stop_tx_timer again.
     * So cancel the timer. There is still a theoretical race condition if
     * the timer is already running and only comes around to check for
     * em485->active_timer when &em485->stop_tx_timer is armed again.
     */
    if (em485->active_timer == &em485->stop_tx_timer)
        hrtimer_try_to_cancel(&em485->stop_tx_timer);

    em485->active_timer = NULL;

    if (em485->tx_stopped) {
        em485->tx_stopped = false;

        up->rs485_start_tx(up);

        if (up->port.rs485.delay_rts_before_send > 0) {
            em485->active_timer = &em485->start_tx_timer;
            start_hrtimer_ms(&em485->start_tx_timer, up->port.rs485.delay_rts_before_send);
            return;
        }
    }

    __start_tx(port);
}

static enum hrtimer_restart serial8250_em485_handle_start_tx(struct hrtimer *t)
{
    struct uart_8250_em485 *em485;
    struct uart_8250_port *p;
    unsigned long flags;

    em485 = container_of(t, struct uart_8250_em485, start_tx_timer);
    p = em485->port;

    spin_lock_irqsave(&p->port.lock, flags);
    if (em485->active_timer == &em485->start_tx_timer) {
        __start_tx(&p->port);
        em485->active_timer = NULL;
    }
    spin_unlock_irqrestore(&p->port.lock, flags);
    return HRTIMER_NORESTART;
}

static void serial8250_start_tx(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    struct uart_8250_em485 *em485 = up->em485;

    serial8250_rpm_get_tx(up);

    if (em485 && em485->active_timer == &em485->start_tx_timer) {
        return;
    }

    if (em485) {
        start_tx_rs485(port);
    } else {
        __start_tx(port);
    }
}

static void serial8250_throttle(struct uart_port *port)
{
    port->throttle(port);
}

static void serial8250_unthrottle(struct uart_port *port)
{
    port->unthrottle(port);
}

static void serial8250_disable_ms(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);

    /* no MSR capabilities */
    if (up->bugs & UART_BUG_NOMSR) {
        return;
    }

    mctrl_gpio_disable_ms(up->gpios);

    up->ier &= ~UART_IER_MSI;
    serial_port_out(port, UART_IER, up->ier);
}

static void serial8250_enable_ms(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);

    /* no MSR capabilities */
    if (up->bugs & UART_BUG_NOMSR) {
        return;
    }

    mctrl_gpio_enable_ms(up->gpios);

    up->ier |= UART_IER_MSI;

    serial8250_rpm_get(up);
    serial_port_out(port, UART_IER, up->ier);
    serial8250_rpm_put(up);
}

void serial8250_read_char(struct uart_8250_port *up, unsigned char lsr)
{
    struct uart_port *port = &up->port;
    unsigned char ch;
    char flag = TTY_NORMAL;

    if (likely(lsr & UART_LSR_DR)) {
        ch = serial_in(up, UART_RX);
    } else {
        /*
         * Intel 82571 has a Serial Over Lan device that will
         * set UART_LSR_BI without setting UART_LSR_DR when
         * it receives a break. To avoid reading from the
         * receive buffer without UART_LSR_DR bit set, we
         * just force the read character to be 0
         */
        ch = 0;
    }

    port->icount.rx++;

    lsr |= up->lsr_saved_flags;
    up->lsr_saved_flags = 0;

    if (unlikely(lsr & UART_LSR_BRK_ERROR_BITS)) {
        if (lsr & UART_LSR_BI) {
            lsr &= ~(UART_LSR_FE | UART_LSR_PE);
            port->icount.brk++;
            /*
             * We do the SysRQ and SAK checking
             * here because otherwise the break
             * may get masked by ignore_status_mask
             * or read_status_mask.
             */
            if (uart_handle_break(port)) {
                return;
            }
        } else if (lsr & UART_LSR_PE) {
            port->icount.parity++;
        } else if (lsr & UART_LSR_FE) {
            port->icount.frame++;
        }
        if (lsr & UART_LSR_OE) {
            port->icount.overrun++;
        }

        /*
         * Mask off conditions which should be ignored.
         */
        lsr &= port->read_status_mask;

        if (lsr & UART_LSR_BI) {
            dev_dbg(port->dev, "handling break\n");
            flag = TTY_BREAK;
        } else if (lsr & UART_LSR_PE) {
            flag = TTY_PARITY;
        } else if (lsr & UART_LSR_FE) {
            flag = TTY_FRAME;
        }
    }
    if (uart_prepare_sysrq_char(port, ch)) {
        return;
    }

    uart_insert_char(port, lsr, UART_LSR_OE, ch, flag);
}
EXPORT_SYMBOL_GPL(serial8250_read_char);

/*
 * serial8250_rx_chars: processes according to the passed in LSR
 * value, and returns the remaining LSR bits not handled
 * by this Rx routine.
 */
unsigned char serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
{
    struct uart_port *port = &up->port;
    int max_count = PORT_ONEHUNDREDFIFTYSIX;

    do {
        serial8250_read_char(up, lsr);
        if (--max_count == 0) {
            break;
        }
        lsr = serial_in(up, UART_LSR);
    } while (lsr & (UART_LSR_DR | UART_LSR_BI));

    tty_flip_buffer_push(&port->state->port);
    return lsr;
}
EXPORT_SYMBOL_GPL(serial8250_rx_chars);

void serial8250_tx_chars(struct uart_8250_port *up)
{
    struct uart_port *port = &up->port;
    struct circ_buf *xmit = &port->state->xmit;
    int count;

    if (port->x_char) {
        uart_xchar_out(port, UART_TX);
        return;
    }
    if (uart_tx_stopped(port)) {
        serial8250_stop_tx(port);
        return;
    }
    if (uart_circ_empty(xmit)) {
        __stop_tx(up);
        return;
    }

    count = up->tx_loadsz;
    do {
        serial_out(up, UART_TX, xmit->buf[xmit->tail]);
        if (up->bugs & UART_BUG_TXRACE) {
            /*
             * The Aspeed BMC virtual UARTs have a bug where data
             * may get stuck in the BMC's Tx FIFO from bursts of
             * writes on the APB interface.
             *
             * Delay back-to-back writes by a read cycle to avoid
             * stalling the VUART. Read a register that won't have
             * side-effects and discard the result.
             */
            serial_in(up, UART_SCR);
        }
        xmit->tail = (xmit->tail + PORT_ONE) & (UART_XMIT_SIZE - PORT_ONE);
        port->icount.tx++;
        if (uart_circ_empty(xmit)) {
            break;
        }
        if ((up->capabilities & UART_CAP_HFIFO) && (serial_in(up, UART_LSR) & BOTH_EMPTY) != BOTH_EMPTY) {
            break;
        }
        /* The BCM2835 MINI UART THRE bit is really a not-full bit. */
        if ((up->capabilities & UART_CAP_MINI) && !(serial_in(up, UART_LSR) & UART_LSR_THRE)) {
            break;
        }
    } while (--count > 0);

    if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) {
        uart_write_wakeup(port);
    }

    /*
     * With RPM enabled, we have to wait until the FIFO is empty before the
     * HW can go idle. So we get here once again with empty FIFO and disable
     * the interrupt and RPM in __stop_tx()
     */
    if (uart_circ_empty(xmit) && !(up->capabilities & UART_CAP_RPM)) {
        __stop_tx(up);
    }
}
EXPORT_SYMBOL_GPL(serial8250_tx_chars);

/* Caller holds uart port lock */
unsigned int serial8250_modem_status(struct uart_8250_port *up)
{
    struct uart_port *port = &up->port;
    unsigned int status = serial_in(up, UART_MSR);

    status |= up->msr_saved_flags;
    up->msr_saved_flags = 0;
    if ((status & UART_MSR_ANY_DELTA) && (up->ier & UART_IER_MSI) && (port->state != NULL)) {
        if (status & UART_MSR_TERI) {
            port->icount.rng++;
        }
        if (status & UART_MSR_DDSR) {
            port->icount.dsr++;
        }
        if (status & UART_MSR_DDCD) {
            uart_handle_dcd_change(port, status & UART_MSR_DCD);
        }
        if (status & UART_MSR_DCTS) {
            uart_handle_cts_change(port, status & UART_MSR_CTS);
        }

        wake_up_interruptible(&port->state->port.delta_msr_wait);
    }

    return status;
}
EXPORT_SYMBOL_GPL(serial8250_modem_status);

static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
{
#ifdef CONFIG_ARCH_ROCKCHIP
    if ((iir & 0xf) != UART_IIR_RX_TIMEOUT) {
        return 0;
    } else {
        return up->dma->rx_dma(up);
    }
#else
    switch (iir & 0x3f) {
        case UART_IIR_RX_TIMEOUT:
            serial8250_rx_dma_flush(up);
            fallthrough;
        case UART_IIR_RLSI:
            return true;
        default:
            break;
    }
    return up->dma->rx_dma(up);
#endif
}

/*
 * This handles the interrupt from one port.
 */
int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
{
    unsigned char status;
    unsigned long flags;
    struct uart_8250_port *up = up_to_u8250p(port);
#ifndef CONFIG_ARCH_ROCKCHIP
    bool skip_rx = false;
#endif
    if (iir & UART_IIR_NO_INT) {
        return 0;
    }
    spin_lock_irqsave(&port->lock, flags);
    status = serial_port_in(port, UART_LSR);
#ifdef CONFIG_ARCH_ROCKCHIP
    if (status & (UART_LSR_DR | UART_LSR_BI)) {
        int dma_err = -1;

        if (up->dma && up->dma->rxchan) {
            dma_err = handle_rx_dma(up, iir);
        }

        if (!up->dma || dma_err) {
            status = serial8250_rx_chars(up, status);
        }
    }
#else
    /*
     * If port is stopped and there are no error conditions in the
     * FIFO, then don't drain the FIFO, as this may lead to TTY buffer
     * overflow. Not servicing, RX FIFO would trigger auto HW flow
     * control when FIFO occupancy reaches preset threshold, thus
     * halting RX. This only works when auto HW flow control is
     * available.
     */
    if (!(status & (UART_LSR_FIFOE | UART_LSR_BRK_ERROR_BITS)) && (port->status & (UPSTAT_AUTOCTS | UPSTAT_AUTORTS)) &&
        !(port->read_status_mask & UART_LSR_DR)) {
        skip_rx = true;
    }

    if ((status & (UART_LSR_DR | UART_LSR_BI)) && !skip_rx) {
        if (!up->dma || handle_rx_dma(up, iir)) {
            status = serial8250_rx_chars(up, status);
        }
    }
#endif
    serial8250_modem_status(up);
#ifdef CONFIG_ARCH_ROCKCHIP
    if ((!up->dma || (up->dma && (!up->dma->txchan || up->dma->tx_err))) && ((iir & 0xf) == UART_IIR_THRI)) {
        serial8250_tx_chars(up);
    }
#else
    if ((!up->dma || (up->dma && up->dma->tx_err)) && (status & UART_LSR_THRE)) {
        serial8250_tx_chars(up);
    }
#endif

#ifdef CONFIG_ARCH_ROCKCHIP
    if (status & UART_LSR_BRK_ERROR_BITS) {
        if (status & UART_LSR_OE) {
            pr_err("%s: Overrun error!\n", port->name);
        }
        if (status & UART_LSR_PE) {
            pr_err("%s: Parity error!\n", port->name);
        }
        if (status & UART_LSR_FE) {
            pr_err("%s: Frame error!\n", port->name);
        }
        if (status & UART_LSR_BI) {
            pr_err("%s: Break interrupt!\n", port->name);
        }

        pr_err("%s: maybe rx pin is low or baudrate is not correct!\n", port->name);
    }
#endif
    uart_unlock_and_check_sysrq(port, flags);
    return 1;
}
EXPORT_SYMBOL_GPL(serial8250_handle_irq);

static int serial8250_default_handle_irq(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned int iir;
    int ret;

    serial8250_rpm_get(up);

    iir = serial_port_in(port, UART_IIR);
    ret = serial8250_handle_irq(port, iir);

    serial8250_rpm_put(up);
    return ret;
}

/*
 * Newer 16550 compatible parts such as the SC16C650 & Altera 16550 Soft IP
 * have a programmable TX threshold that triggers the THRE interrupt in
 * the IIR register. In this case, the THRE interrupt indicates the FIFO
 * has space available. Load it up with tx_loadsz bytes.
 */
static int serial8250_tx_threshold_handle_irq(struct uart_port *port)
{
    unsigned long flags;
    unsigned int iir = serial_port_in(port, UART_IIR);
    /* TX Threshold IRQ triggered so load up FIFO */
    if ((iir & UART_IIR_ID) == UART_IIR_THRI) {
        struct uart_8250_port *up = up_to_u8250p(port);

        spin_lock_irqsave(&port->lock, flags);
        serial8250_tx_chars(up);
        spin_unlock_irqrestore(&port->lock, flags);
    }

    iir = serial_port_in(port, UART_IIR);
    return serial8250_handle_irq(port, iir);
}

static unsigned int serial8250_tx_empty(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned long flags;
    unsigned int lsr;

    serial8250_rpm_get(up);

    spin_lock_irqsave(&port->lock, flags);
    lsr = serial_port_in(port, UART_LSR);
    up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
    spin_unlock_irqrestore(&port->lock, flags);

    serial8250_rpm_put(up);

    return (lsr & BOTH_EMPTY) == BOTH_EMPTY ? TIOCSER_TEMT : 0;
}

unsigned int serial8250_do_get_mctrl(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned int status;
    unsigned int val;

    serial8250_rpm_get(up);
    status = serial8250_modem_status(up);
    serial8250_rpm_put(up);

    val = serial8250_MSR_to_TIOCM(status);
    if (up->gpios) {
        return mctrl_gpio_get(up->gpios, &val);
    }

    return val;
}
EXPORT_SYMBOL_GPL(serial8250_do_get_mctrl);

static unsigned int serial8250_get_mctrl(struct uart_port *port)
{
    if (port->get_mctrl) {
        return port->get_mctrl(port);
    }
    return serial8250_do_get_mctrl(port);
}

void serial8250_do_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned char mcr;

    mcr = serial8250_TIOCM_to_MCR(mctrl);

    mcr = (mcr & up->mcr_mask) | up->mcr_force | up->mcr;

    serial8250_out_MCR(up, mcr);
}
EXPORT_SYMBOL_GPL(serial8250_do_set_mctrl);

static void serial8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
    if (port->set_mctrl) {
        port->set_mctrl(port, mctrl);
    } else {
        serial8250_do_set_mctrl(port, mctrl);
    }
}

static void serial8250_break_ctl(struct uart_port *port, int break_state)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned long flags;

    serial8250_rpm_get(up);
    spin_lock_irqsave(&port->lock, flags);
    if (break_state == -1) {
        up->lcr |= UART_LCR_SBC;
    } else {
        up->lcr &= ~UART_LCR_SBC;
    }
    serial_port_out(port, UART_LCR, up->lcr);
    spin_unlock_irqrestore(&port->lock, flags);
    serial8250_rpm_put(up);
}

/*
 *    Wait for transmitter & holding register to empty
 */
static void wait_for_xmitr(struct uart_8250_port *up, int bits)
{
    unsigned int status, tmout = PORT_TENTHOUSAND;

    /* Wait up to 10ms for the character(s) to be sent. */
    for (;;) {
        status = serial_in(up, UART_LSR);

        up->lsr_saved_flags |= status & LSR_SAVE_FLAGS;

        if ((status & bits) == bits) {
            break;
        }
        if (--tmout == 0) {
            break;
        }
        udelay(1);
        touch_nmi_watchdog();
    }

    /* Wait up to 1s for flow control if necessary */
    if (up->port.flags & UPF_CONS_FLOW) {
        for (tmout = PORT_ONETHOUSANDTHOUSAND; tmout; tmout--) {
            unsigned int msr = serial_in(up, UART_MSR);
            up->msr_saved_flags |= msr & MSR_SAVE_FLAGS;
            if (msr & UART_MSR_CTS) {
                break;
            }
            udelay(1);
            touch_nmi_watchdog();
        }
    }
}

#ifdef CONFIG_CONSOLE_POLL
/*
 * Console polling routines for writing and reading from the uart while
 * in an interrupt or debug context.
 */

static int serial8250_get_poll_char(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned char lsr;
    int status;

    serial8250_rpm_get(up);
    lsr = serial_port_in(port, UART_LSR);
    if (!(lsr & UART_LSR_DR)) {
        status = NO_POLL_CHAR;
        goto out;
    }

    status = serial_port_in(port, UART_RX);
out:
    serial8250_rpm_put(up);
    return status;
}

static void serial8250_put_poll_char(struct uart_port *port, unsigned char c)
{
    unsigned int ier;
    struct uart_8250_port *up = up_to_u8250p(port);

    serial8250_rpm_get(up);
    /*
     *    First save the IER then disable the interrupts
     */
    ier = serial_port_in(port, UART_IER);
    if (up->capabilities & UART_CAP_UUE) {
        serial_port_out(port, UART_IER, UART_IER_UUE);
    } else {
        serial_port_out(port, UART_IER, 0);
    }

    wait_for_xmitr(up, BOTH_EMPTY);
    /*
     *    Send the character out.
     */
    serial_port_out(port, UART_TX, c);

    /*
     *    Finally, wait for transmitter to become empty
     *    and restore the IER
     */
    wait_for_xmitr(up, BOTH_EMPTY);
    serial_port_out(port, UART_IER, ier);
    serial8250_rpm_put(up);
}

#endif /* CONFIG_CONSOLE_POLL */

int serial8250_do_startup(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned long flags;
    unsigned char lsr, iir;
    int retval;

    if (!port->fifosize) {
        port->fifosize = uart_config[port->type].fifo_size;
    }
    if (!up->tx_loadsz) {
        up->tx_loadsz = uart_config[port->type].tx_loadsz;
    }
    if (!up->capabilities) {
        up->capabilities = uart_config[port->type].flags;
    }
    up->mcr = 0;

    if (port->iotype != up->cur_iotype) {
        set_io_from_upio(port);
    }

    serial8250_rpm_get(up);
    if (port->type == PORT_16C950) {
        /* Wake up and initialize UART */
        up->acr = 0;
        serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
        serial_port_out(port, UART_EFR, UART_EFR_ECB);
        serial_port_out(port, UART_IER, 0);
        serial_port_out(port, UART_LCR, 0);
        serial_icr_write(up, UART_CSR, 0); /* Reset the UART */
        serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
        serial_port_out(port, UART_EFR, UART_EFR_ECB);
        serial_port_out(port, UART_LCR, 0);
    }

    if (port->type == PORT_DA830) {
        /* Reset the port */
        serial_port_out(port, UART_IER, 0);
        serial_port_out(port, UART_DA830_PWREMU_MGMT, 0);
        mdelay(0xa);

        /* Enable Tx, Rx and free run mode */
        serial_port_out(port, UART_DA830_PWREMU_MGMT,
                        UART_DA830_PWREMU_MGMT_UTRST | UART_DA830_PWREMU_MGMT_URRST | UART_DA830_PWREMU_MGMT_FREE);
    }

    if (port->type == PORT_NPCM) {
        /*
         * Nuvoton calls the scratch register 'UART_TOR' (timeout
         * register). Enable it, and set TIOC (timeout interrupt
         * comparator) to be 0x20 for correct operation.
         */
        serial_port_out(port, UART_NPCM_TOR, UART_NPCM_TOIE | 0x20);
    }

#ifdef CONFIG_SERIAL_8250_RSA
    /*
     * If this is an RSA port, see if we can kick it up to the
     * higher speed clock.
     */
    enable_rsa(up);
#endif

    /*
     * Clear the FIFO buffers and disable them.
     * (they will be reenabled in set_termios())
     */
    serial8250_clear_fifos(up);

    /*
     * Clear the interrupt registers.
     */
    serial_port_in(port, UART_LSR);
    serial_port_in(port, UART_RX);
    serial_port_in(port, UART_IIR);
    serial_port_in(port, UART_MSR);

    /*
     * At this point, there's no way the LSR could still be 0xff;
     * if it is, then bail out, because there's likely no UART
     * here.
     */
    if (!(port->flags & UPF_BUGGY_UART) && (serial_port_in(port, UART_LSR) == 0xff)) {
        dev_info_ratelimited(port->dev, "LSR safety check engaged!\n");
        retval = -ENODEV;
        goto out;
    }

    /*
     * For a XR16C850, we need to set the trigger levels
     */
    if (port->type == PORT_16850) {
        unsigned char fctr;

        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);

        fctr = serial_in(up, UART_FCTR) & ~(UART_FCTR_RX | UART_FCTR_TX);
        serial_port_out(port, UART_FCTR, fctr | UART_FCTR_TRGD | UART_FCTR_RX);
        serial_port_out(port, UART_TRG, UART_TRG_96);
        serial_port_out(port, UART_FCTR, fctr | UART_FCTR_TRGD | UART_FCTR_TX);
        serial_port_out(port, UART_TRG, UART_TRG_96);

        serial_port_out(port, UART_LCR, 0);
    }

    /*
     * For the Altera 16550 variants, set TX threshold trigger level.
     */
    if (((port->type == PORT_ALTR_16550_F32) || (port->type == PORT_ALTR_16550_F64) ||
         (port->type == PORT_ALTR_16550_F128)) &&
        (port->fifosize > PORT_ONE)) {
        /* Bounds checking of TX threshold (valid 0 to fifosize-2) */
        if ((up->tx_loadsz < 2) || (up->tx_loadsz > port->fifosize)) {
            dev_err(port->dev, "TX FIFO Threshold errors, skipping\n");
        } else {
            serial_port_out(port, UART_ALTR_AFR, UART_ALTR_EN_TXFIFO_LW);
            serial_port_out(port, UART_ALTR_TX_LOW, port->fifosize - up->tx_loadsz);
            port->handle_irq = serial8250_tx_threshold_handle_irq;
        }
    }

    /* Check if we need to have shared IRQs */
    if (port->irq && (up->port.flags & UPF_SHARE_IRQ)) {
        up->port.irqflags |= IRQF_SHARED;
    }

    if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) {
        unsigned char iir1;

        if (port->irqflags & IRQF_SHARED) {
            disable_irq_nosync(port->irq);
        }

        /*
         * Test for UARTs that do not reassert THRE when the
         * transmitter is idle and the interrupt has already
         * been cleared.  Real 16550s should always reassert
         * this interrupt whenever the transmitter is idle and
         * the interrupt is enabled.  Delays are necessary to
         * allow register changes to become visible.
         */
        spin_lock_irqsave(&port->lock, flags);

        wait_for_xmitr(up, UART_LSR_THRE);
        serial_port_out_sync(port, UART_IER, UART_IER_THRI);
        udelay(1); /* allow THRE to set */
        iir1 = serial_port_in(port, UART_IIR);
        serial_port_out(port, UART_IER, 0);
        serial_port_out_sync(port, UART_IER, UART_IER_THRI);
        udelay(1); /* allow a working UART time to re-assert THRE */
        iir = serial_port_in(port, UART_IIR);
        serial_port_out(port, UART_IER, 0);

        spin_unlock_irqrestore(&port->lock, flags);

        if (port->irqflags & IRQF_SHARED) {
            enable_irq(port->irq);
        }

        /*
         * If the interrupt is not reasserted, or we otherwise
         * don't trust the iir, setup a timer to kick the UART
         * on a regular basis.
         */
        if ((!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) || (up->port.flags & UPF_BUG_THRE)) {
            up->bugs |= UART_BUG_THRE;
        }
    }

    retval = up->ops->setup_irq(up);
    if (retval) {
        goto out;
    }

    /*
     * Now, initialize the UART
     */
    serial_port_out(port, UART_LCR, UART_LCR_WLEN8);

    spin_lock_irqsave(&port->lock, flags);
    if (up->port.flags & UPF_FOURPORT) {
        if (!up->port.irq) {
            up->port.mctrl |= TIOCM_OUT1;
        }
    } else
        /*
         * Most PC uarts need OUT2 raised to enable interrupts.
         */
        if (port->irq) {
            up->port.mctrl |= TIOCM_OUT2;
        }

    serial8250_set_mctrl(port, port->mctrl);

    /*
     * Serial over Lan (SoL) hack:
     * Intel 8257x Gigabit ethernet chips have a 16550 emulation, to be
     * used for Serial Over Lan.  Those chips take a longer time than a
     * normal serial device to signalize that a transmission data was
     * queued. Due to that, the above test generally fails. One solution
     * would be to delay the reading of iir. However, this is not
     * reliable, since the timeout is variable. So, let's just don't
     * test if we receive TX irq.  This way, we'll never enable
     * UART_BUG_TXEN.
     */
    if (up->port.quirks & UPQ_NO_TXEN_TEST) {
        goto dont_test_tx_en;
    }

    /*
     * Do a quick test to see if we receive an interrupt when we enable
     * the TX irq.
     */
    serial_port_out(port, UART_IER, UART_IER_THRI);
    lsr = serial_port_in(port, UART_LSR);
    iir = serial_port_in(port, UART_IIR);
    serial_port_out(port, UART_IER, 0);

    if ((lsr & UART_LSR_TEMT) && (iir & UART_IIR_NO_INT)) {
        if (!(up->bugs & UART_BUG_TXEN)) {
            up->bugs |= UART_BUG_TXEN;
            dev_dbg(port->dev, "enabling bad tx status workarounds\n");
        }
    } else {
        up->bugs &= ~UART_BUG_TXEN;
    }

dont_test_tx_en:
    spin_unlock_irqrestore(&port->lock, flags);

    /*
     * Clear the interrupt registers again for luck, and clear the
     * saved flags to avoid getting false values from polling
     * routines or the previous session.
     */
    serial_port_in(port, UART_LSR);
    serial_port_in(port, UART_RX);
    serial_port_in(port, UART_IIR);
    serial_port_in(port, UART_MSR);
    up->lsr_saved_flags = 0;
    up->msr_saved_flags = 0;

    /*
     * Request DMA channels for both RX and TX.
     */
    if (up->dma) {
        const char *msg = NULL;

        if (uart_console(port)) {
            msg = "forbid DMA for kernel console";
        } else if (serial8250_request_dma(up)) {
#ifdef CONFIG_ARCH_ROCKCHIP
            msg = "failed to request DMA, use interrupt mode";
#else
            msg = "failed to request DMA";
#endif
        }
        if (msg) {
            dev_warn_ratelimited(port->dev, "%s\n", msg);
            up->dma = NULL;
        }
    }

    /*
     * Set the IER shadow for rx interrupts but defer actual interrupt
     * enable until after the FIFOs are enabled; otherwise, an already-
     * active sender can swamp the interrupt handler with "too much work".
     */
    up->ier = UART_IER_RLSI | UART_IER_RDI;

    if (port->flags & UPF_FOURPORT) {
        unsigned int icp;
        /*
         * Enable interrupts on the AST Fourport board
         */
        icp = (port->iobase & 0xfe0) | 0x01f;
        outb_p(0x80, icp);
        inb_p(icp);
    }
    retval = 0;
out:
    serial8250_rpm_put(up);
    return retval;
}
EXPORT_SYMBOL_GPL(serial8250_do_startup);

static int serial8250_startup(struct uart_port *port)
{
    if (port->startup) {
        return port->startup(port);
    }
    return serial8250_do_startup(port);
}

void serial8250_do_shutdown(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned long flags;

    serial8250_rpm_get(up);
    /*
     * Disable interrupts from this port
     */
    spin_lock_irqsave(&port->lock, flags);
    up->ier = 0;
    serial_port_out(port, UART_IER, 0);
    spin_unlock_irqrestore(&port->lock, flags);

    synchronize_irq(port->irq);

    if (up->dma) {
        serial8250_release_dma(up);
    }

    spin_lock_irqsave(&port->lock, flags);
    if (port->flags & UPF_FOURPORT) {
        /* reset interrupts on the AST Fourport board */
        inb((port->iobase & 0xfe0) | 0x1f);
        port->mctrl |= TIOCM_OUT1;
    } else {
        port->mctrl &= ~TIOCM_OUT2;
    }

    serial8250_set_mctrl(port, port->mctrl);
    spin_unlock_irqrestore(&port->lock, flags);

    /*
     * Disable break condition and FIFOs
     */
    serial_port_out(port, UART_LCR, serial_port_in(port, UART_LCR) & ~UART_LCR_SBC);
    serial8250_clear_fifos(up);

#ifdef CONFIG_SERIAL_8250_RSA
    /*
     * Reset the RSA board back to 115kbps compat mode.
     */
    disable_rsa(up);
#endif

    /*
     * Read data port to reset things, and then unlink from
     * the IRQ chain.
     */
    serial_port_in(port, UART_RX);
    serial8250_rpm_put(up);

    up->ops->release_irq(up);
}
EXPORT_SYMBOL_GPL(serial8250_do_shutdown);

static void serial8250_shutdown(struct uart_port *port)
{
    if (port->shutdown) {
        port->shutdown(port);
    } else {
        serial8250_do_shutdown(port);
    }
}

/* Nuvoton NPCM UARTs have a custom divisor calculation */
static unsigned int npcm_get_divisor(struct uart_8250_port *up, unsigned int baud)
{
    struct uart_port *port = &up->port;

    return DIV_ROUND_CLOSEST(port->uartclk, PORT_SIXTEEN * baud + 0x2) - 0x2;
}

static unsigned int serial8250_do_get_divisor(struct uart_port *port, unsigned int baud, unsigned int *frac)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned int quot;

    /*
     * Handle magic divisors for baud rates above baud_base on
     * SMSC SuperIO chips.
     *
     */
    if ((port->flags & UPF_MAGIC_MULTIPLIER) && baud == (port->uartclk / 0x4)) {
        quot = 0x8001;
    } else if ((port->flags & UPF_MAGIC_MULTIPLIER) && baud == (port->uartclk / 0x8)) {
        quot = 0x8002;
    } else if (up->port.type == PORT_NPCM) {
        quot = npcm_get_divisor(up, baud);
    } else {
        quot = uart_get_divisor(port, baud);
    }

    /*
     * Oxford Semi 952 rev B workaround
     */
    if ((up->bugs & UART_BUG_QUOT) && ((quot & 0xff) == 0)) {
        quot++;
    }

    return quot;
}

static unsigned int serial8250_get_divisor(struct uart_port *port, unsigned int baud, unsigned int *frac)
{
    if (port->get_divisor) {
        return port->get_divisor(port, baud, frac);
    }

    return serial8250_do_get_divisor(port, baud, frac);
}

static unsigned char serial8250_compute_lcr(struct uart_8250_port *up, tcflag_t c_cflag)
{
    unsigned char cval;

    switch (c_cflag & CSIZE) {
        case CS5:
            cval = UART_LCR_WLEN5;
            break;
        case CS6:
            cval = UART_LCR_WLEN6;
            break;
        case CS7:
            cval = UART_LCR_WLEN7;
            break;
        default:
        case CS8:
            cval = UART_LCR_WLEN8;
            break;
    }

    if (c_cflag & CSTOPB) {
        cval |= UART_LCR_STOP;
    }
    if (c_cflag & PARENB) {
        cval |= UART_LCR_PARITY;
        if (up->bugs & UART_BUG_PARITY) {
            up->fifo_bug = true;
        }
    }
    if (!(c_cflag & PARODD)) {
        cval |= UART_LCR_EPAR;
    }
#ifdef CMSPAR
    if (c_cflag & CMSPAR) {
        cval |= UART_LCR_SPAR;
    }
#endif

    return cval;
}

void serial8250_do_set_divisor(struct uart_port *port, unsigned int baud, unsigned int quot, unsigned int quot_frac)
{
    struct uart_8250_port *up = up_to_u8250p(port);

#ifdef CONFIG_ARCH_ROCKCHIP
    serial_port_out(port, UART_MCR, UART_MCR_LOOP);
#endif

    /* Workaround to enable 115200 baud on OMAP1510 internal ports */
    if (is_omap1510_8250(up)) {
        if (baud == 0x1c200) {
            quot = 1;
            serial_port_out(port, UART_OMAP_OSC_12M_SEL, 1);
        } else {
            serial_port_out(port, UART_OMAP_OSC_12M_SEL, 0);
        }
    }

    /*
     * For NatSemi, switch to bank 2 not bank 1, to avoid resetting EXCR2,
     * otherwise just set DLAB
     */
    if (up->capabilities & UART_NATSEMI) {
        serial_port_out(port, UART_LCR, 0xe0);
    } else {
        serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);
    }

    serial_dl_write(up, quot);
#ifdef CONFIG_ARCH_ROCKCHIP
    if (quot != serial_dl_read(up)) {
        dev_warn_ratelimited(port->dev, "ttyS%d set divisor fail, quot:%d != dll,dlh:%d\n", serial_index(port), quot,
                             serial_dl_read(up));
    }
#endif
    if (port->type != PORT_16750) {
        serial_port_out(port, UART_LCR, up->lcr); /* reset DLAB */
    }

#ifdef CONFIG_ARCH_ROCKCHIP
    serial_port_out(port, UART_MCR, up->mcr);
#endif
}
EXPORT_SYMBOL_GPL(serial8250_do_set_divisor);

static void serial8250_set_divisor(struct uart_port *port, unsigned int baud, unsigned int quot, unsigned int quot_frac)
{
    if (port->set_divisor) {
        port->set_divisor(port, baud, quot, quot_frac);
    } else {
        serial8250_do_set_divisor(port, baud, quot, quot_frac);
    }
}

static unsigned int serial8250_get_baud_rate(struct uart_port *port, struct ktermios *termios, struct ktermios *old)
{
    unsigned int tolerance = port->uartclk / 0x64;
    unsigned int min;
    unsigned int max;

    /*
     * Handle magic divisors for baud rates above baud_base on SMSC
     * Super I/O chips.  Enable custom rates of clk/4 and clk/8, but
     * disable divisor values beyond 32767, which are unavailable.
     */
    if (port->flags & UPF_MAGIC_MULTIPLIER) {
        min = ((port->uartclk / PORT_SIXTEEN) / UART_DIV_MAX) >> 1;
        max = (port->uartclk + tolerance) / 0x4;
    } else {
        min = (port->uartclk / PORT_SIXTEEN) / UART_DIV_MAX;
        max = (port->uartclk + tolerance) / PORT_SIXTEEN;
    }

    /*
     * Ask the core to calculate the divisor for us.
     * Allow 1% tolerance at the upper limit so uart clks marginally
     * slower than nominal still match standard baud rates without
     * causing transmission errors.
     */
    return uart_get_baud_rate(port, termios, old, min, max);
}

/*
 * Note in order to avoid the tty port mutex deadlock don't use the next method
 * within the uart port callbacks. Primarily it's supposed to be utilized to
 * handle a sudden reference clock rate change.
 */
void serial8250_update_uartclk(struct uart_port *port, unsigned int uartclk)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    struct tty_port *tport = &port->state->port;
    unsigned int baud, quot, frac = 0;
    struct ktermios *termios;
    struct tty_struct *tty;
    unsigned long flags;

    tty = tty_port_tty_get(tport);
    if (!tty) {
        mutex_lock(&tport->mutex);
        port->uartclk = uartclk;
        mutex_unlock(&tport->mutex);
        return;
    }

    down_write(&tty->termios_rwsem);
    mutex_lock(&tport->mutex);

    if (port->uartclk == uartclk) {
        goto out_lock;
    }

    port->uartclk = uartclk;

    if (!tty_port_initialized(tport)) {
        goto out_lock;
    }

    termios = &tty->termios;

    baud = serial8250_get_baud_rate(port, termios, NULL);
    quot = serial8250_get_divisor(port, baud, &frac);

    serial8250_rpm_get(up);
    spin_lock_irqsave(&port->lock, flags);

    uart_update_timeout(port, termios->c_cflag, baud);

    serial8250_set_divisor(port, baud, quot, frac);
    serial_port_out(port, UART_LCR, up->lcr);

    spin_unlock_irqrestore(&port->lock, flags);
    serial8250_rpm_put(up);

out_lock:
    mutex_unlock(&tport->mutex);
    up_write(&tty->termios_rwsem);
    tty_kref_put(tty);
}
EXPORT_SYMBOL_GPL(serial8250_update_uartclk);

void serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    unsigned char cval;
    unsigned long flags;
    unsigned int baud, quot, frac = 0;

    if (up->capabilities & UART_CAP_MINI) {
        termios->c_cflag &= ~(CSTOPB | PARENB | PARODD | CMSPAR);
        if ((termios->c_cflag & CSIZE) == CS5 || (termios->c_cflag & CSIZE) == CS6) {
            termios->c_cflag = (termios->c_cflag & ~CSIZE) | CS7;
        }
    }
    cval = serial8250_compute_lcr(up, termios->c_cflag);

    baud = serial8250_get_baud_rate(port, termios, old);
    quot = serial8250_get_divisor(port, baud, &frac);

    /*
     * Ok, we're now changing the port state.  Do it with
     * interrupts disabled.
     */
    serial8250_rpm_get(up);
    spin_lock_irqsave(&port->lock, flags);

    up->lcr = cval; /* Save computed LCR */

    if ((up->capabilities & UART_CAP_FIFO) && (port->fifosize > 1)) {
        /* NOTE: If fifo_bug is not set, a user can set RX_trigger. */
        if ((baud < 0x960 && !up->dma) || up->fifo_bug) {
            up->fcr &= ~UART_FCR_TRIGGER_MASK;
            up->fcr |= UART_FCR_TRIGGER_1;
        }
    }

    /*
     * MCR-based auto flow control.  When AFE is enabled, RTS will be
     * deasserted when the receive FIFO contains more characters than
     * the trigger, or the MCR RTS bit is cleared.
     */
    if (up->capabilities & UART_CAP_AFE) {
        up->mcr &= ~UART_MCR_AFE;
        if (termios->c_cflag & CRTSCTS) {
            up->mcr |= UART_MCR_AFE;
        }
    }

    /*
     * Update the per-port timeout.
     */
    uart_update_timeout(port, termios->c_cflag, baud);

    port->read_status_mask = UART_LSR_OE | UART_LSR_THRE | UART_LSR_DR;
    if (termios->c_iflag & INPCK) {
        port->read_status_mask |= UART_LSR_FE | UART_LSR_PE;
    }
    if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK)) {
        port->read_status_mask |= UART_LSR_BI;
    }

    /*
     * Characteres to ignore
     */
    port->ignore_status_mask = 0;
    if (termios->c_iflag & IGNPAR) {
        port->ignore_status_mask |= UART_LSR_PE | UART_LSR_FE;
    }
    if (termios->c_iflag & IGNBRK) {
        port->ignore_status_mask |= UART_LSR_BI;
        /*
         * If we're ignoring parity and break indicators,
         * ignore overruns too (for real raw support).
         */
        if (termios->c_iflag & IGNPAR) {
            port->ignore_status_mask |= UART_LSR_OE;
        }
    }

    /*
     * ignore all characters if CREAD is not set
     */
    if ((termios->c_cflag & CREAD) == 0) {
        port->ignore_status_mask |= UART_LSR_DR;
    }

#ifndef CONFIG_ARCH_ROCKCHIP
    /*
     * CTS flow control flag and modem status interrupts
     */
    up->ier &= ~UART_IER_MSI;
    if (!(up->bugs & UART_BUG_NOMSR) && UART_ENABLE_MS(&up->port, termios->c_cflag)) {
        up->ier |= UART_IER_MSI;
    }
    if (up->capabilities & UART_CAP_UUE) {
        up->ier |= UART_IER_UUE;
    }
    if (up->capabilities & UART_CAP_RTOIE) {
        up->ier |= UART_IER_RTOIE;
    }

    serial_port_out(port, UART_IER, up->ier);
#endif

    if (up->capabilities & UART_CAP_EFR) {
        unsigned char efr = 0;
        /*
         * TI16C752/Startech hardware flow control.
         * - TI16C752 requires control thresholds to be set.
         * - UART_MCR_RTS is ineffective if auto-RTS mode is enabled.
         */
        if (termios->c_cflag & CRTSCTS) {
            efr |= UART_EFR_CTS;
        }

        serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
        if (port->flags & UPF_EXAR_EFR) {
            serial_port_out(port, UART_XR_EFR, efr);
        } else {
            serial_port_out(port, UART_EFR, efr);
        }
    }

#ifdef CONFIG_ARCH_ROCKCHIP
    /* Reset uart to make sure it is idle, then set baud rate */
    serial_port_out(port, 0x88 >> 0x2, 0x7);
#endif

    serial8250_set_divisor(port, baud, quot, frac);

#ifdef CONFIG_ARCH_ROCKCHIP
    up->fcr = UART_FCR_ENABLE_FIFO | UART_FCR_T_TRIG_10 | UART_FCR_R_TRIG_10;
#endif
    /*
     * LCR DLAB must be set to enable 64-byte FIFO mode. If the FCR
     * is written without DLAB set, this mode will be disabled.
     */
    if (port->type == PORT_16750) {
        serial_port_out(port, UART_FCR, up->fcr);
        serial_port_out(port, UART_LCR, up->lcr); /* reset DLAB */
    }

    if (port->type != PORT_16750) {
        /* emulated UARTs (Lucent Venus 167x) need two steps */
        if (up->fcr & UART_FCR_ENABLE_FIFO) {
            serial_port_out(port, UART_FCR, UART_FCR_ENABLE_FIFO);
        }
        serial_port_out(port, UART_FCR, up->fcr); /* set fcr */
    }
    serial8250_set_mctrl(port, port->mctrl);

#ifdef CONFIG_ARCH_ROCKCHIP
    /*
     * CTS flow control flag and modem status interrupts
     */
    up->ier &= ~UART_IER_MSI;
    if (!(up->bugs & UART_BUG_NOMSR) && UART_ENABLE_MS(&up->port, termios->c_cflag)) {
        up->ier |= UART_IER_MSI;
    }
    if (up->capabilities & UART_CAP_UUE) {
        up->ier |= UART_IER_UUE;
    }
    if (up->capabilities & UART_CAP_RTOIE) {
        up->ier |= UART_IER_RTOIE;
    }

    serial_port_out(port, UART_IER, up->ier);
#endif

    spin_unlock_irqrestore(&port->lock, flags);
    serial8250_rpm_put(up);

    /* Don't rewrite B0 */
    if (tty_termios_baud_rate(termios)) {
        tty_termios_encode_baud_rate(termios, baud, baud);
    }
}
EXPORT_SYMBOL(serial8250_do_set_termios);

static void serial8250_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old)
{
    if (port->set_termios) {
        port->set_termios(port, termios, old);
    } else {
        serial8250_do_set_termios(port, termios, old);
    }
}

void serial8250_do_set_ldisc(struct uart_port *port, struct ktermios *termios)
{
    if (termios->c_line == N_PPS) {
        port->flags |= UPF_HARDPPS_CD;
        spin_lock_irq(&port->lock);
        serial8250_enable_ms(port);
        spin_unlock_irq(&port->lock);
    } else {
        port->flags &= ~UPF_HARDPPS_CD;
        if (!UART_ENABLE_MS(port, termios->c_cflag)) {
            spin_lock_irq(&port->lock);
            serial8250_disable_ms(port);
            spin_unlock_irq(&port->lock);
        }
    }
}
EXPORT_SYMBOL_GPL(serial8250_do_set_ldisc);

static void serial8250_set_ldisc(struct uart_port *port, struct ktermios *termios)
{
    if (port->set_ldisc) {
        port->set_ldisc(port, termios);
    } else {
        serial8250_do_set_ldisc(port, termios);
    }
}

void serial8250_do_pm(struct uart_port *port, unsigned int state, unsigned int oldstate)
{
    struct uart_8250_port *p = up_to_u8250p(port);

    serial8250_set_sleep(p, state != 0);
}
EXPORT_SYMBOL(serial8250_do_pm);

static void serial8250_pm(struct uart_port *port, unsigned int state, unsigned int oldstate)
{
    if (port->pm) {
        port->pm(port, state, oldstate);
    } else {
        serial8250_do_pm(port, state, oldstate);
    }
}

static unsigned int serial8250_port_size(struct uart_8250_port *pt)
{
    if (pt->port.mapsize) {
        return pt->port.mapsize;
    }
    if (pt->port.iotype == UPIO_AU) {
        if (pt->port.type == PORT_RT2880) {
            return 0x100;
        }
        return 0x1000;
    }
    if (is_omap1_8250(pt)) {
        return 0x16 << pt->port.regshift;
    }

    return 0x8 << pt->port.regshift;
}

/*
 * Resource handling.
 */
static int serial8250_request_std_resource(struct uart_8250_port *up)
{
    unsigned int size = serial8250_port_size(up);
    struct uart_port *port = &up->port;
    int ret = 0;

    switch (port->iotype) {
        case UPIO_AU:
        case UPIO_TSI:
        case UPIO_MEM32:
        case UPIO_MEM32BE:
        case UPIO_MEM16:
        case UPIO_MEM:
            if (!port->mapbase) {
                ret = -EINVAL;
                break;
            }

            if (!request_mem_region(port->mapbase, size, "serial")) {
                ret = -EBUSY;
                break;
            }

            if (port->flags & UPF_IOREMAP) {
                port->membase = ioremap(port->mapbase, size);
                if (!port->membase) {
                    release_mem_region(port->mapbase, size);
                    ret = -ENOMEM;
                }
            }
            break;

        case UPIO_HUB6:
        case UPIO_PORT:
            if (!request_region(port->iobase, size, "serial")) {
                ret = -EBUSY;
            }
            break;
    }
    return ret;
}

static void serial8250_release_std_resource(struct uart_8250_port *up)
{
    unsigned int size = serial8250_port_size(up);
    struct uart_port *port = &up->port;

    switch (port->iotype) {
        case UPIO_AU:
        case UPIO_TSI:
        case UPIO_MEM32:
        case UPIO_MEM32BE:
        case UPIO_MEM16:
        case UPIO_MEM:
            if (!port->mapbase) {
                break;
            }

            if (port->flags & UPF_IOREMAP) {
                iounmap(port->membase);
                port->membase = NULL;
            }

            release_mem_region(port->mapbase, size);
            break;

        case UPIO_HUB6:
        case UPIO_PORT:
            release_region(port->iobase, size);
            break;
    }
}

static void serial8250_release_port(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);

    serial8250_release_std_resource(up);
}

static int serial8250_request_port(struct uart_port *port)
{
    struct uart_8250_port *up = up_to_u8250p(port);

    return serial8250_request_std_resource(up);
}

static int fcr_get_rxtrig_bytes(struct uart_8250_port *up)
{
    const struct serial8250_config *conf_type = &uart_config[up->port.type];
    unsigned char bytes;

    bytes = conf_type->rxtrig_bytes[UART_FCR_R_TRIG_BITS(up->fcr)];

    return bytes ? bytes : -EOPNOTSUPP;
}

static int bytes_to_fcr_rxtrig(struct uart_8250_port *up, unsigned char bytes)
{
    const struct serial8250_config *conf_type = &uart_config[up->port.type];
    int i;

    if (!conf_type->rxtrig_bytes[UART_FCR_R_TRIG_BITS(UART_FCR_R_TRIG_00)]) {
        return -EOPNOTSUPP;
    }

    for (i = 1; i < UART_FCR_R_TRIG_MAX_STATE; i++) {
        if (bytes < conf_type->rxtrig_bytes[i]) {
            /* Use the nearest lower value */
            return (--i) << UART_FCR_R_TRIG_SHIFT;
        }
    }

    return UART_FCR_R_TRIG_11;
}

static int do_get_rxtrig(struct tty_port *port)
{
    struct uart_state *state = container_of(port, struct uart_state, port);
    struct uart_port *uport = state->uart_port;
    struct uart_8250_port *up = up_to_u8250p(uport);

    if (!(up->capabilities & UART_CAP_FIFO) || uport->fifosize <= 1) {
        return -EINVAL;
    }

    return fcr_get_rxtrig_bytes(up);
}

static int do_serial8250_get_rxtrig(struct tty_port *port)
{
    int rxtrig_bytes;

    mutex_lock(&port->mutex);
    rxtrig_bytes = do_get_rxtrig(port);
    mutex_unlock(&port->mutex);

    return rxtrig_bytes;
}

static ssize_t rx_trig_bytes_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct tty_port *port = dev_get_drvdata(dev);
    int rxtrig_bytes;

    rxtrig_bytes = do_serial8250_get_rxtrig(port);
    if (rxtrig_bytes < 0) {
        return rxtrig_bytes;
    }

    return snprintf(buf, PAGE_SIZE, "%d\n", rxtrig_bytes);
}

static int do_set_rxtrig(struct tty_port *port, unsigned char bytes)
{
    struct uart_state *state = container_of(port, struct uart_state, port);
    struct uart_port *uport = state->uart_port;
    struct uart_8250_port *up = up_to_u8250p(uport);
    int rxtrig;

    if (!(up->capabilities & UART_CAP_FIFO) || uport->fifosize <= 1 || up->fifo_bug) {
        return -EINVAL;
    }

    rxtrig = bytes_to_fcr_rxtrig(up, bytes);
    if (rxtrig < 0) {
        return rxtrig;
    }

    serial8250_clear_fifos(up);
    up->fcr &= ~UART_FCR_TRIGGER_MASK;
    up->fcr |= (unsigned char)rxtrig;
    serial_out(up, UART_FCR, up->fcr);
    return 0;
}

static int do_serial8250_set_rxtrig(struct tty_port *port, unsigned char bytes)
{
    int ret;

    mutex_lock(&port->mutex);
    ret = do_set_rxtrig(port, bytes);
    mutex_unlock(&port->mutex);

    return ret;
}

static ssize_t rx_trig_bytes_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
    struct tty_port *port = dev_get_drvdata(dev);
    unsigned char bytes;
    int ret;

    if (!count) {
        return -EINVAL;
    }

    ret = kstrtou8(buf, 0xa, &bytes);
    if (ret < 0) {
        return ret;
    }

    ret = do_serial8250_set_rxtrig(port, bytes);
    if (ret < 0) {
        return ret;
    }

    return count;
}

static DEVICE_ATTR_RW(rx_trig_bytes);

static struct attribute *serial8250_dev_attrs[] = {&dev_attr_rx_trig_bytes.attr, NULL};

static struct attribute_group serial8250_dev_attr_group = {
    .attrs = serial8250_dev_attrs,
};

static void register_dev_spec_attr_grp(struct uart_8250_port *up)
{
    const struct serial8250_config *conf_type = &uart_config[up->port.type];

    if (conf_type->rxtrig_bytes[0]) {
        up->port.attr_group = &serial8250_dev_attr_group;
    }
}

static void serial8250_config_port(struct uart_port *port, int flags)
{
    struct uart_8250_port *up = up_to_u8250p(port);
    int ret;

    /*
     * Find the region that we can probe for.  This in turn
     * tells us whether we can probe for the type of port.
     */
    ret = serial8250_request_std_resource(up);
    if (ret < 0) {
        return;
    }

    if (port->iotype != up->cur_iotype) {
        set_io_from_upio(port);
    }

    if (flags & UART_CONFIG_TYPE) {
        autoconfig(up);
    }

    if (port->rs485.flags & SER_RS485_ENABLED) {
        port->rs485_config(port, &port->rs485);
    }

    /* if access method is AU, it is a 16550 with a quirk */
    if (port->type == PORT_16550A && port->iotype == UPIO_AU) {
        up->bugs |= UART_BUG_NOMSR;
    }

    /* HW bugs may trigger IRQ while IIR == NO_INT */
    if (port->type == PORT_TEGRA) {
        up->bugs |= UART_BUG_NOMSR;
    }

    if ((port->type != PORT_UNKNOWN) && (flags & UART_CONFIG_IRQ)) {
        autoconfig_irq(up);
    }

    if (port->type == PORT_UNKNOWN) {
        serial8250_release_std_resource(up);
    }

    register_dev_spec_attr_grp(up);
    up->fcr = uart_config[up->port.type].fcr;
}

static int serial8250_verify_port(struct uart_port *port, struct serial_struct *ser)
{
    if (ser->irq >= nr_irqs || ser->irq < 0 || ser->baud_base < 0x2580 || ser->type < PORT_UNKNOWN ||
        ser->type >= ARRAY_SIZE(uart_config) || ser->type == PORT_CIRRUS || ser->type == PORT_STARTECH) {
        return -EINVAL;
    }
    return 0;
}

static const char *serial8250_type(struct uart_port *port)
{
    int type = port->type;

    if (type >= ARRAY_SIZE(uart_config)) {
        type = 0;
    }
    return uart_config[type].name;
}

static const struct uart_ops serial8250_pops = {
    .tx_empty = serial8250_tx_empty,
    .set_mctrl = serial8250_set_mctrl,
    .get_mctrl = serial8250_get_mctrl,
    .stop_tx = serial8250_stop_tx,
    .start_tx = serial8250_start_tx,
    .throttle = serial8250_throttle,
    .unthrottle = serial8250_unthrottle,
    .stop_rx = serial8250_stop_rx,
    .enable_ms = serial8250_enable_ms,
    .break_ctl = serial8250_break_ctl,
    .startup = serial8250_startup,
    .shutdown = serial8250_shutdown,
    .set_termios = serial8250_set_termios,
    .set_ldisc = serial8250_set_ldisc,
    .pm = serial8250_pm,
    .type = serial8250_type,
    .release_port = serial8250_release_port,
    .request_port = serial8250_request_port,
    .config_port = serial8250_config_port,
    .verify_port = serial8250_verify_port,
#ifdef CONFIG_CONSOLE_POLL
    .poll_get_char = serial8250_get_poll_char,
    .poll_put_char = serial8250_put_poll_char,
#endif
};

void serial8250_init_port(struct uart_8250_port *up)
{
    struct uart_port *port = &up->port;

    spin_lock_init(&port->lock);
    port->ops = &serial8250_pops;
    port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE);

    up->cur_iotype = 0xFF;
}
EXPORT_SYMBOL_GPL(serial8250_init_port);

void serial8250_set_defaults(struct uart_8250_port *up)
{
    struct uart_port *port = &up->port;

    if (up->port.flags & UPF_FIXED_TYPE) {
        unsigned int type = up->port.type;

        if (!up->port.fifosize) {
            up->port.fifosize = uart_config[type].fifo_size;
        }
        if (!up->tx_loadsz) {
            up->tx_loadsz = uart_config[type].tx_loadsz;
        }
        if (!up->capabilities) {
            up->capabilities = uart_config[type].flags;
        }
    }

    set_io_from_upio(port);

    /* default dma handlers */
    if (up->dma) {
        if (!up->dma->tx_dma) {
            up->dma->tx_dma = serial8250_tx_dma;
        }
        if (!up->dma->rx_dma) {
            up->dma->rx_dma = serial8250_rx_dma;
        }
    }
}
EXPORT_SYMBOL_GPL(serial8250_set_defaults);

#ifdef CONFIG_SERIAL_8250_CONSOLE

static void serial8250_console_putchar(struct uart_port *port, int ch)
{
    struct uart_8250_port *up = up_to_u8250p(port);

    wait_for_xmitr(up, UART_LSR_THRE);
    serial_port_out(port, UART_TX, ch);
}

/*
 *    Restore serial console when h/w power-off detected
 */
static void serial8250_console_restore(struct uart_8250_port *up)
{
    struct uart_port *port = &up->port;
    struct ktermios termios;
    unsigned int baud, quot, frac = 0;

    termios.c_cflag = port->cons->cflag;
    if (port->state->port.tty && termios.c_cflag == 0) {
        termios.c_cflag = port->state->port.tty->termios.c_cflag;
    }

    baud = serial8250_get_baud_rate(port, &termios, NULL);
    quot = serial8250_get_divisor(port, baud, &frac);

    serial8250_set_divisor(port, baud, quot, frac);
    serial_port_out(port, UART_LCR, up->lcr);
    serial8250_out_MCR(up, up->mcr | UART_MCR_DTR | UART_MCR_RTS);
}

/*
 *    Print a string to the serial port trying not to disturb
 *    any possible real use of the port...
 *
 *    The console_lock must be held when we get here.
 *
 *    Doing runtime PM is really a bad idea for the kernel console.
 *    Thus, we assume the function is called when device is powered up.
 */
void serial8250_console_write(struct uart_8250_port *up, const char *s, unsigned int count)
{
    struct uart_8250_em485 *em485 = up->em485;
    struct uart_port *port = &up->port;
    unsigned long flags;
    unsigned int ier;
    int locked = 1;

    touch_nmi_watchdog();

    if (oops_in_progress) {
        locked = spin_trylock_irqsave(&port->lock, flags);
    } else {
        spin_lock_irqsave(&port->lock, flags);
    }

    /*
     *    First save the IER then disable the interrupts
     */
    ier = serial_port_in(port, UART_IER);

    if (up->capabilities & UART_CAP_UUE) {
        serial_port_out(port, UART_IER, UART_IER_UUE);
    } else {
        serial_port_out(port, UART_IER, 0);
    }

    /* check scratch reg to see if port powered off during system sleep */
    if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) {
        serial8250_console_restore(up);
        up->canary = 0;
    }

    if (em485) {
        if (em485->tx_stopped) {
            up->rs485_start_tx(up);
        }
        mdelay(port->rs485.delay_rts_before_send);
    }

    uart_console_write(port, s, count, serial8250_console_putchar);

    /*
     *    Finally, wait for transmitter to become empty
     *    and restore the IER
     */
    wait_for_xmitr(up, BOTH_EMPTY);

    if (em485) {
        mdelay(port->rs485.delay_rts_after_send);
        if (em485->tx_stopped) {
            up->rs485_stop_tx(up);
        }
    }

    serial_port_out(port, UART_IER, ier);

    /*
     *    The receive handling will happen properly because the
     *    receive ready bit will still be set; it is not cleared
     *    on read.  However, modem control will not, we must
     *    call it if we have saved something in the saved flags
     *    while processing with interrupts off.
     */
    if (up->msr_saved_flags) {
        serial8250_modem_status(up);
    }

    if (locked) {
        spin_unlock_irqrestore(&port->lock, flags);
    }
}

static unsigned int probe_baud(struct uart_port *port)
{
    unsigned char lcr, dll, dlm;
    unsigned int quot;

    lcr = serial_port_in(port, UART_LCR);
    serial_port_out(port, UART_LCR, lcr | UART_LCR_DLAB);
    dll = serial_port_in(port, UART_DLL);
    dlm = serial_port_in(port, UART_DLM);
    serial_port_out(port, UART_LCR, lcr);

    quot = (dlm << 0x8) | dll;
    return (port->uartclk / PORT_SIXTEEN) / quot;
}

int serial8250_console_setup(struct uart_port *port, char *options, bool probe)
{
    int baud = 9600;
    int bits = 8;
    int parity = 'n';
    int flow = 'n';
    int ret;

    if (!port->iobase && !port->membase) {
        return -ENODEV;
    }

    if (options) {
        uart_parse_options(options, &baud, &parity, &bits, &flow);
    } else if (probe) {
        baud = probe_baud(port);
    }

    ret = uart_set_options(port, port->cons, baud, parity, bits, flow);
    if (ret) {
        return ret;
    }

    if (port->dev) {
        pm_runtime_get_sync(port->dev);
    }

    return 0;
}

int serial8250_console_exit(struct uart_port *port)
{
    if (port->dev) {
        pm_runtime_put_sync(port->dev);
    }

    return 0;
}

#endif /* CONFIG_SERIAL_8250_CONSOLE */

MODULE_LICENSE("GPL");
